• Clinton, before impeachment proceedings, looks straight into the TV cameras to utter the most famous line of his presidency: "I did not have sexual relations with that woman."
• An impeached Nixon, hands held high, fingers spread in a V-for-victory sign, boards a helicopter on the White House lawn to leave the White House, the first and only president to have resigned in office.
• Johnson, eligible to run for president again but so unpopular he is about to lose the Wisconsin primary to little-known Minnesota Sen. Eugene McCarthy, announces on TV, "I shall not seek, and I will not accept, the nomination of my party for another term as your president."
Even generally successful presidents have faced humiliating episodes: for Reagan, the Iran-contra scandal; for Dwight Eisenhower, the U-2 spy plane episode. But there's a difference between difficulty and debacle.
"Generalizations are tricky," says Mr. Greenberg, whose 2003 book, "Nixon's Shadow: The History of an Image," examined one second-termer. "When we start looking at the evidence, there's not a lot to substantiate the notion."
How can you distinguish between the problems presidents encounter in every term and ones that discredit the entire four years? What's the standard for gauging any president's success?
Even those who have tried to develop measures are cautious about generalizing. In their book, "Addressing the State of the Union," University of Northern Iowa professor Donna Hoffman and Dominican University of California assistant professor Alison Howard use one such tool: calculating how many legislative requests presidents make of Congress — and how many get adopted in the next session.
Critics often deride State of the Union messages — "empty rhetoric," some said after last year's. In fact, modern presidents include specific calls for congressional action — the median is about 31, according to Ms. Hoffman and Ms. Howard, ranging from Carter's 1979 low of nine to Clinton's 2000 high of 87.
On the surface, the numbers might seem to substantiate the difficulties of a second term. Hoffman and Howard's research shows 43 percent of the requests are passed in some form — 51 percent in a first term and only 38.6 percent in the second.
But the issue is more complicated than that, especially when considering early presidents. The nation's early leaders weren't much concerned with legislative requests. Not until Woodrow Wilson did the notion emerge of presidents as what Hoffman calls "legislators in chief."
"When measuring success, I'm not concerned about whether Jefferson got Congress to do what he wanted," she says. "[To him] it would have been anathema."
Greenberg agrees. The intense focus on 1600 Pennsylvania Avenue is relatively recent. "If you were a reporter in the 19th century, you didn't go over to the White House," he says. "You went to the Senate gallery."
Focusing too closely on what chief executives get through Congress can lead to misconceptions about modern presidents, too. Legislation is only one of their tools. Others include federal agencies, executive orders, appointments, and judicial nominations. Hoffman and Greenberg cite both Reagan and Clinton as success stories.
"You hear people saying [Clinton] squandered his second term," says Greenberg. "He did a lot. Not through legislation. But that's a narrow view of what presidents do." He cites one example: Clinton's executive orders protecting more wilderness areas from development "than any president since Teddy Roosevelt."
"Meanwhile," Greenberg adds, "budget deficits gave way to surpluses, the economy enjoyed its longest continuous expansion [in history], and poverty rates plummeted."
It's important to disentangle ideology from the questions of success and failure. Unlike basketball, in which success means getting the most points, success to a Democrat — like passing health reform — can mean abysmal failure to a Republican, and vice versa.
The two sides disagree not just on worth but facts. Greenberg, not a Reagan admirer, praises Reagan's greatest second-term achievement — his partnership with Russia's Mikhail Gorbachev to peacefully end the cold war.
" 'Star wars' had nothing to do with it," he says, rebutting the idea that Reagan cowed Gorbachev into submission by pushing a strategic defense shield. "Russia couldn't maintain client states. Reagan was not cynical about Gorbachev. His overtures in the second term revived a hopeful spirit."
Sharply disagreeing about the importance of star wars is Clark Judge, a former speechwriter and aide to both Reagan and George H.W. Bush.
"Yes, the Soviets were [getting] weaker and knew it," says Mr. Judge, now managing director of White House Writers Group, a consulting firm. "Star wars figured into this by making a first-strike capacity obsolete." He describes a variety of early Reagan-era moves strengthening NATO. "All contributed to the realization of how tenuous their position was."
Judge also argues forcefully for other Reagan second-term achievements: "tax reform, holding the line on spending, [supporting] a large number of countries to move from despotism to democracy, and fidelity to judicial restraint."
When Hoffman and Howard measure success, they do it from the view of the president. But a 12 percent difference between first- and second-term legislative success doesn't seem enough to warrant a term like "curse" — or determine whether second-term presidents fail or just falter.
One interesting take on the issue comes not from a professional historian but an Indiana real estate agent, Alfred Zacher, whose lifelong passion has been the study of second terms. His self-published book tries to catalog whether presidential second terms were "successful," "troubled," or "failed." He counts only five failures: Grant, Cleveland, Johnson, Nixon, and Bush.
The problems that recurrently surface for presidents — whether in their first term or second — seem to be the same four:
Unpopular wars. Truman in Korea, Johnson and Nixon in Vietnam, and Bush in Iraq — their second terms all included war or military action Americans disliked.
Bad economies. The 1987 stock market crash hurt Reagan, and the broader economic collapse in 2008 marred Bush's legacy. But the 1873 and 1893 recessions in Grant's and Cleveland's respective second terms were enormous setbacks, too.
Personal scandal or corruption. The Monica Lewinsky affair led to Clinton's impeachment, and Nixon's ordering of the Watergate coverup resulted in his impeachment and resignation.
Grant was hobbled by the appointment of a Treasury secretary who turned out to be a crook. Reagan eventually took the blame for Iran-contra, though it's unclear how sharply he had focused on the issue.
Jefferson's problems with one member of his administration may have been in a class of their own: His first-term vice president, Aaron Burr, killed Alexander Hamilton in a duel and later, after being jettisoned from the administration, was tried for treason for supposedly fomenting revolution on the Western frontier. The controversies surrounding Burr, and Jefferson's handling of them, no doubt affected his popularity.
Perils of divided government. Historians today praise a Monroe administration treaty with Britain that would have called slavery "piracy" as well as the president's efforts to keep native Americans on lands they inhabited. A hostile Congress rejected both.
The Senate killed one of Wilson's signature initiatives — American membership in the League of Nations. A Republican House blocked many of Clinton's legislative efforts.
Then there was F.D.R.
"He had a disastrous first half" to his second term, says Jeff Shesol, author of "Supreme Power," which chronicles F.D.R.'s fight with a hostile Congress and Supreme Court.
The root of F.D.R.'s problems had come in his first four years. The court had blocked so many of his New Deal programs that after reelection he concocted a plan to "pack" the court by increasing the number of justices. The Senate rejected his efforts.
Facing a deep recession in 1938, F.D.R. used the midterm elections to try purging the Senate of his enemies; the effort failed. "After that, the Senate was dead set against him," says Mr. Shesol. Fortunately for F.D.R., by 1939 Americans were preoccupied with war in Europe. Domestic worries receded.
"If it hadn't been for World War II," Shesol says, "we'd say he had a successful first term but the second was a squandered opportunity."
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The image of F.D.R. then versus now highlights another point about legacies: how Americans see presidents through a glass darkly. Coolidge finished his second term immensely popular, but historians fault him for not doing more to prevent the Depression. Jefferson and Truman left office vastly unpopular. Historians and the public are more reverential today.
Time will influence Obama's reputation, too. As he prepares to place his hand on the Bible and take the oath of office for the second time, what problems might he face?
Most commentators discount the possibility of a personal moral scandal from a president who mentions his wife and daughters in speech after speech. And they are dubious about his taste for entering into the kind of trillion-dollar-plus war of choice that Iraq turned out to be.
The economy? In one sense good news lies ahead. Even during the campaign, many financial analysts predicted that, while the economy might weaken in 2013, the US should experience at least modest job growth over the next four years no matter who won the election. Congress and the White House have also agreed to part of a "fiscal cliff" deal — an increase in income taxes for the very rich.
Still, Democrats and Republicans differ sharply over how to cut government spending and extend the debt ceiling. Whatever agreements emerge over those issues, there's no question that Obama will move through his second term without the money to fund everything — like infrastructure — on his domestic agenda.
And as happens with every president, some of the big events of the second term will take everyone by surprise: Think 9/11, hurricane Katrina, and the Arab Spring.
Yet history offers lessons about how to surmount various problems in a second term. In Obama's case, two seem worth exploring.
The first is divided government.
Shesol thinks F.D.R.'s second term is particularly instructive for Obama, also facing a hostile Congress and court, but not necessarily because it should teach him to avoid what is often offered as the reason for F.D.R.'s mistakes: hubris.
"If this was hubris, so was Social Security," says Shesol, noting that the court-packing vote was close and F.D.R. might have won with a little more compromise. "This was risk-taking."
To him, more plausible is that, lulled by a landslide in 1936, F.D.R. departed in his second term from his usual pattern. "He had an utter willingness to draw people in," Shesol says of F.D.R.'s first term. "To build coalitions, to bring members of Congress into the White House and make them think his ideas were their ideas."
Could more of that from Obama ease the bitter conflict that dominated much of his first term? "I'd advise him to start wooing members of Congress," says Judge. "Accept compromise. Republicans now believe the president is out to destroy the Republican Party."
Of course, Democrats argue that the president has been too quick to compromise — 34 percent of them in one recent poll about tax cuts. Does ideology play a role here, too?
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Sitting by the window in his Chesapeake Bay house late one rainy morning, former Michigan Democratic Rep. David Bonior thinks about the divide between Republicans and Democrats. It's a subject he knows something about, having served 13 terms in Congress, including as former majority and minority whip (and, full disclosure, 20 years ago, as this writer's boss).
Mr. Bonior was part of a hostile Democratic majority under Reagan. Who better to know how presidents should handle a hostile Congress? How could Reagan get so much done in the early 1980s when Democrats had as big a majority as Republicans have now?
To Bonior, that's no mystery. "Understand the ideological structure," he says. "Republicans are more homogeneous. It's easier to go shopping for Democrats [on votes] because we're ideologically more diverse."
He points to another element. "Besides, Reagan's big victory was tax cuts. Tip [O'Neill] tried hard to stop them. It's not hard to cut taxes."
The criticism Obama gets for not cultivating Congress more doesn't come just from Republicans. "He's not a schmoozer," Sen. Claire McCaskill (D) of Missouri said recently.
Bonior believes personal relationships matter. "Clinton was magnificent at it," he says. "George [H.W.] Bush liked Congress. He'd come down to the gym and play handball with Sonny Montgomery, a Democrat. I liked him."
Did this make things easier on issues on which they agreed? Yes, Bonior says, mentioning times when he worked with the Reagan White House on Central American issues. But then he remembers with relish a speech he made on the House floor that infuriated Bush. Personal relationships only go so far when lawmakers passionately disagree.
Bonior admires Obama. What seems to worry him more than his reaching out to Republicans is Obama's relationship with his own party. "Check this," he says. He mentions the number of fundraisers Obama attended for Democratic House candidates. It's a low number. "If he did more we might be eight seats down [instead of 20]," Bonior says. "And money isn't the only way. It's a phone call: 'Congressman, you have a call from the president. He wants to chat. Get your ideas.' "
He remembers being invited to Camp David during the Clinton years, though he had fought his own president over the North American Free Trade Agreement. "You're eating breakfast with Clinton. He's throwing balls to his dog. You're honored to be there," he says.
In fairness, Hoffman and Howard have analyzed Obama's first term numbers in getting legislation through Congress. They find him succeeding at above the median rate. Even after Republicans took control of the House in 2010, his rate only went down to a "respectable" 42.7 percent.
Still, the lesson is clear. Even those who admire Obama think he could reach out more.
There's a second area in which history might be instructive: foreign affairs. In his 2009 Nobel Peace Prize address, Obama called his accomplishments abroad "slim," adding "in part this is because I am at the beginning, not the end, of my labors on the world stage."
Presidents often look abroad to burnish their legacy in second terms. Obama, limited at home by fiscal-cliff agreements, might follow that pattern. There's no shortage of tasks: blocking Iran's nuclear program without going to war, moving Arab countries toward democracies, withdrawn from a stable Afghanistan, forging an arms agreement with Russia, renewing a focus on Asia that maintains relations with China.
Could Clinton's second term be a model?
Samuel "Sandy" Berger was national security adviser in Clinton's second term. Now chair of a consulting firm he formed with Madeleine Albright, Clinton's former secretary of State, he ticks off the three tools presidents use to shape foreign policy: "Defense is one tool; diplomacy and development are the others," he says — and then notes how hard it will be to make progress using any of them.
Take, for example, Obama's effort to nudge Arab countries toward democracy. Why can't he do as well as the Clinton administration did when it stabilized countries after the collapse of the Soviet Union? "We had something [Obama] won't have — hundreds of millions of dollars for assistance," Mr. Berger says. "Obama won't have the money to stabilize democracies, to pour into Egypt or Libya."
The money worries that dominate the fiscal-cliff debate are broader than domestic issues. Berger worries generally about retrenchment. "Americans are weary of war," he says. "Clearly we have to address domestic problems. But at the exclusion of problems in the world?"
He cites talk of cutting the State Department budget. "We need to engage more, not less. Not everything is costly. Diplomacy is not costly. But if we cut further, we can't operate in the world."
Berger praises a lot of what Obama accomplished in the first term. "His cardinal achievement was bringing down our involvement in Afghanistan, ending the war in Iraq — and progress against Al Qaeda."
Concerned about the delay in taking the lead during the Arab Spring, he knows administrations learn from experience because his did. He cites Bosnia. "We held back. Didn't lead. After two years we took the lead. Got to the negotiating table at Dayton. That taught us a valuable lesson when it came to Kosovo."
He's hopeful Obama's second term will see him defer less to the Europeans. "Where we lead matters," he says.
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That bridge to the 21st century concerning speechwriter Waldman stayed in the inaugural. In one of his last speeches, Clinton told the White House Correspondents' Association dinner he was preparing his resume. He pretended to tick off a bunch of things he'd done. One was "Designed, built, and painted bridge to the 21st century." It got a big laugh.
Whether or not Clinton upended the "existing order," no curse held him back. In the 21 second terms beginning with George Washington's, obstacles recur. But a curse? Even the least successful presidents do a lot to build their bridges to the future.
More to the point is something Reagan said when he gave the farewell speech at the end of his second term.
Reagan's writers gave him a story to help make a point — of a moment early in his tenure when sailors on an American ship in the South China Sea spotted a boat low in the water, crammed with Vietnamese refugees.
A sailor watched as the boat drew closer. Finally, one of the refugees stood up and called, "Hello, Freedom Man."
Reagan doesn't drive home his obvious belief: that his administration helped bring freedom to people around the world. His claim is more modest — one that, unlike claims of a curse, is true of every president, and will be true of Obama.
"We weren't just marking time," Reagan said. "We made a difference."