As he campaigned against racial integration in the 1960s, George Wallace complained "there's not a dime's worth of difference" between the Democratic and Republican parties. But nowadays that's only true in primary elections, which is why this week marks such a dramatic and unpredictable shift in the race for the White House.
Strange as it sounds, the first five months of the 2008 campaign have lacked the most powerful force in contemporary politics: partisanship.
John McCain bested a field of Republicans who almost unanimously shared his support for the Iraq War, embrace of President Bush's tax cuts, skepticism toward government-run health care and opposition to abortion rights. Barack Obama outlasted Hillary Clinton in a Democratic competition staking out the opposite ground. (Check out my exclusive interview with Obama in the first video clip).
Now those two self-contained conversations have given way to the broad clash of familiar product lines: Republican conservatism and Democratic liberalism. Mr. McCain rides the tide of recent American history; Mr. Obama surfs the wave that has crested in opposition to George W. Bush's presidency.
The effects of those cross-currents on voters--those following the campaign closely, and those who haven't yet tuned in--remain impossible to forecast.
It's no surprise that Mr. Wallace saw so little difference between Republicans and Democrats. The two parties each harbored a variegated mix of ideological types.
Great Society liberals like Lyndon Johnson flew under the Democratic banner with segregationists like Mr. Wallace. Even as Barry Goldwater led the rise of the Republican right, Senate GOP Leader Everett Dirksen helped LBJ pass civil rights legislation.