By now the 2008 Democratic primary battle between Barack Obama and Hillary Clinton, which concludes Tuesday with contests in Montana and South Dakota, has developed a story line so reliable pundits can recite it in their sleep.
The first African American and first woman with solid chances to win the White House have split the Democratic party nearly in half – his coalition of young voters, affluent liberals and African-Americans against her coalition of women, older voters, Hispanics and working class whites.
Mr. Obama appears on track to a narrow nomination victory if he can win over just a small fraction of the roughly 200 superdelegates still undecided.
But that numbing familiarity can't obscure what makes this nomination fight unique. In its cost, duration, competitiveness, and breadth of citizen involvement, it stands alone in the history of American presidential politics.
"We've had higher rates of participation, not just by voting but by volunteering and giving, than any other" such contest, says Michael Malbin, executive director of the Campaign Finance Institute and a one-time Congressional aide to then-Rep. Dick Cheney. "And there's nothing that's remotely close."
A springtime gauntlet of primaries became part of the presidential nominating process a century ago as Progressive Era reformers sought to give voters, rather than party bosses, a greater voice. That voice was initially muted; as recently as 1968, Vice President Hubert Humphrey won the Democratic nomination without entering any of that year's 15 primaries.
But in the Obama-Clinton contest, voters have shouted louder and longer than ever beginning with the Iowa caucuses on Jan. 3. The primary calendar is two months longer than in 1968.
Shattering previous records, the two leading Democrats raised nearly $500-million through April for deploying their rival armies. Mrs. Clinton's $214-million, according to the Center for Responsive Politics, exceeds money raised by all candidates in both parties in the hard-fought 1988 contests that nominated George H.W. Bush and Michael Dukakis. Mr. Obama raised $50-million more than she did, relying heavily on the Internet and creating a new model for financial supremacy.
"The scale of this thing is just extraordinary," says Tony Corrado, a Colby College professor and leading authority on campaign fund-raising. What makes their performance all the more striking, he notes, is one past argument used in explaining the dominance of white male candidates. Women and minority politicians, skeptics once asserted, "didn't have the sort of social-business networks" needed to compete.
Moreover, each top Democrat has proven resilient enough to defy the normal laws of political gravity. In nomination fights over the past two decades, such formidable challengers as Bob Dole, Richard Gephardt, John McCain, Bill Bradley and Howard Dean have all faded after early defeats – the way John Edwards, Mitt Romney and Rudy Giuliani did this year.
But Mrs. Clinton has finished robustly despite a costly string of February losses. Even after the weekend disappointment of failing to gain all the Michigan and Florida delegates she had sought before the Democratic Party's Rules and Bylaws Committee, Mrs. Clinton commands holds 45% of convention delegates to Mr. Obama's 49%.
Just as remarkable, the intensity of competition has been inversely proportional to the ideological stakes. In the roiling Democratic battle of 1968, Eugene McCarthy and Robert Kennedy challenged Mr. Humphrey and Lyndon Johnson over the Vietnam War; in 1976, Ronald Reagan carried the banner of ascendant GOP conservatism against incumbent President Gerald Ford; in 1980, Edward Kennedy y fought incumbent President Jimmy Carter in defense of traditional liberalism.