The discomfiting question now being confronted by Democrats, who desperately want change in Washington, is whether the thirst for change in the party might imperil its front-runner, not help her.

We all know the advantages that former President Bill Clinton confers on Hillary Clinton’s presidential campaign. He has the star power, the easy elegance, the great smile, plus he carries a reminder that the financial markets can roar even if the big-government, high-tax, pro-regulation, vaguely anti-business party is in power. Michelle Obama, who possesses a refreshing late baby boomer informality, and Elizabeth Edwards, who is admired by everyone on Earth but Ann Coulter, are terrific assets, but as candidate spouses go, Mr. Clinton is in a class by himself. Even his detractors say so.

But there is also a downside to Mr. Clinton’s appearance at his wife’s side, and Sen. Barack Obama has subtly but unmistakably identified it. “What we’re more interested in is looking forward,” he said in an interview with The Associated Press, “not in looking backward.”

There was a lot that the American people liked about the Clinton years. There was the economy, to start. There was the way the president engaged with the world, winning admirers for the United States and winning trust among world leaders. There was the open embrace of diversity, seeing our differences as a strength rather than using them as a wedge and transforming them into a weakness.

Goodbye to all that

But on Jan. 20, 2001, Americans basically said: Goodbye to all that. And by that they meant tawdry fund-raising efforts, mind-numbing, hair-splitting semantic arguments, the Clinton marriage melodrama and the president’s wandering eye, for which no optometric remedy was known. The Bush Republicans have not been saints in the money-and-politics arena, but there has been no quibbling about the definition of “is,” no histrionics in the White House private quarters, no cheap romances just off the Oval Office.

Sen. Clinton remains the Democrats’ front-runner, with gobs of money (though not quite as much as Sen. Obama in the second quarter of 2007), formidable endorsements, mastery of the issues, more than a quarter-century of engagement in the important domestic questions of the age and, of course, the best strategist since Marcus Alonzo Hannah, the magus who actually managed to make William McKinley appealing to the American people.

She opposes the war in Iraq. But so does Obama. She is skeptical of the Bush economic strategy. But so is Obama. She personifies change. But so does Obama.

The underside of Mr. Obama’s campaign is that he is too young, too inexperienced, to serve as chief executive. The underside of Ms. Clinton’s campaign is that she is too close to Mr. Clinton and, an irony and oddity for someone who is relatively new to political office and who represents a new phenomenon in American politics, too familiar a figure.

Power pact?

There is a whispering campaign going on as the campaign revs up, and it’s not the usual one – about busted marriages or shaky finances or unsound resumes. This whispering campaign involves people who are all but ashamed to say it, but who nonetheless believe there was a power-sharing pact in the Clinton marriage and who don’t think the New York senator ought to get a turn at power just because she and her husband made some kind of bargain about the presidency.

This would not be the “corrupt bargain” (that was the alleged agreement between John Quincy Adams and Henry Clay that gave the former the presidency and the latter the job of secretary of state in 1824), but the conjugal bargain.

Sen. Obama is cloaking his campaign-trail language in the rhetoric of change, but his intention is unambiguous. And it is part of a great American tradition: The No. 2 candidate almost always assails the top candidate for being the choice of the bosses and big-shots, and also for being for a little bit of change but not for a whole lot of change. Sen. Gary W. Hart of Colorado nearly wrestled the Democratic presidential nomination away from former Vice President Walter F. Mondale of Minnesota with that tactic in 1984.

Head vs. heart

There is another dynamic at work in Democratic politics 2008. Sen. Clinton is clearly the candidate of the head. She is logical, methodical, thoughtful. Sen. Obama is clearly the candidate of the heart. He appeals to the romance of politics, to its sense of possibility. These two candidates both are from Illinois. She carries the whiff of Gov. Adlai E. Stevenson, intellectual and guarded. He carries the whiff of Sen. Paul Douglas, civil rights crusader, environmentalist and reformer. Both would like to be Abraham Lincoln, but even Abraham Lincoln wasn’t Abraham Lincoln in 1859.

This could go on for a while, and it probably should. Both candidates have enough money to fight it out for months. Both need to gain sea legs as presidential candidates. Both have to figure out how much change they are for and how they would achieve it. The two most powerful words in American politics are “had enough”; the Republicans used them in 1946 to take over Congress. The Democrats may use them in 2008.

But not all winds of change blow in favor of Hillary Clinton. The country has had enough in 2008, but the threat to her candidacy is that the voters had had enough back in 2000, too, and they might not invite another Clinton into the White House. Running as a change agent has its opportunities, but also its perils.