Of all life's ironies, this may be among the most unusual, the most awkward and the most significant.

For much of his life, Albert Gore Jr. was prepared, or was preparing, for the presidency. The first time he ran, in 1988, he seemed almost too young. The second time, in 2000, he seemed almost too old. Now that he realizes the great gold ring is beyond his powers, he finds himself with the power to determine who might grasp that ring, or at least the 2008 Democratic nomination.

Because it may be true that the only person in the United States who can bring the 2008 primary campaign to a halt is Mr. Gore -- and he knows it.

A decade ago he seemed the stiffest of the stiff. Today, as an advocate for the environment with a Nobel and an Oscar on his resume, he is the coolest of the cool. His sermons sometimes won blank stares in the Senate and in the vice presidency. They win rapt attention now. When Mr. Gore -- who once skewered himself by being carted around a stage on a mover's dolly as if he were a plank of wood -- spoke, millions yawned. Today when Mr. Gore speaks, millions listen.

Sen. Hillary Rodham Clinton of New York can still win the Democratic nomination; Sen. Barack Obama of Illinois hasn't clinched it yet, and indeed remains far from what the sports writers call the "magic number" that ends a pennant race. Mrs. Clinton fights fiercely, and her life story shows that she doesn't possess the genes to quit. But if New Mexico Gov. Bill Richardson's endorsement of Mr. Obama dealt a serious blow to Mrs. Clinton's electoral credibility, then Mr. Gore's could be fatal.

As the drumbeat to push Mrs. Clinton out of the race increases, Mr. Gore is weighing whether to speak out -- one way or the other.

But first a few words about the essential Gore, who, like Mrs. Clinton, has been transformed into a cartoon and is rarely understood as a human being.

For someone so often regarded as having been bred for the presidency, he is a breed apart: more a dreamer and a seeker than a planner and a schemer, and yet always -- always -- dutiful and disciplined.

He is at once rebellious (only a rebel would have endorsed Gov. Howard Dean of Vermont for president in 2004) and deeply loyal (only a loyalist would have stood by President Bill Clinton so prominently during the impeachment crisis at the end of the last century). He is at once obsessed with the past (nothing moves him quite so deeply as tales of courage from the civil-rights movement) and obsessed with the future (which explains his crusade against global warming). He is at once a traditionalist (he and his wife fought smut in popular culture) and an early adopter (he had a computer long before most politicians, and was the first mainstream pol with a BlackBerry).

Mr. Gore -- deeply serious in public, wickedly funny in private -- is at once deeply cerebral (he once held a dinner party to discuss the metaphor) and deeply emotional (talk to him sometime about the canoe ride he took with his father after the elder Gore lost his Senate re-election battle in 1970). He is at once a team player (he described President Bush as "my commander in chief" less than a year after Mr. Bush lost the popular vote to him but was awarded the presidency) and an individual (he was a lone wolf in taking on the chemical companies after the Love Canal and Times Beach environmental catastrophes).

He fought to be on Bill Clinton's national ticket in 1992 after watching the Arkansas governor take his 1988 profile (Southern moderate) and his 1988 strategy (play down Iowa, make a stand in New Hampshire, clean up on Super Tuesday) and take it to the nomination. He fought Mrs. Clinton for influence in the White House. He was deeply offended by Mr. Clinton's conduct in the Oval Office, willingly endured the catcalls and the criticism when he didn't invite Mr. Clinton to take part in the 2000 campaign and then, convinced that Mr. Clinton's behavior had doomed his presidential hopes, stoically endured the quadrennial Democratic spectacle of an angry party turning on the nominee it had selected with confetti-and-balloons enthusiasm only four months earlier.

Now, insert this deeply complex, deeply conflicted but somehow liberated symbol of the baby-boom generation -- remember that politicians seek the presidency so as to win a Nobel Prize, not the other way around -- into the deeply complex, deeply conflicted political situation the Democrats face today.

Some people who know Mr. Gore believe he will intercede, tell Mrs. Clinton that she cannot win and must, for the good of the party she seeks to lead, stand down. Some believe he will hold his tongue, knowing that such an intercession might diminish him by appearing to settle a score.

No other American of modern times has made a comeback quite as dramatic as Mr. Gore's, with the possible exception of Richard Nixon, who was denied the presidency in 1960 and awarded it in 1968 and again in 1972. No other American of modern times has proved the point so clearly as Mr. Gore that policy is more important than politics.

Mr. Gore's greatest moments of political joy came during those heady days of the 1992 campaign when he and his wife bused through the countryside with the Clintons. Those who know Mr. Gore say that Mr. Obama's insurgency, designed to sweep away old politics, is just the sort of movement that Mr. Gore applauds. Read his recent book, "The Assault on Reason," and you will see why.

Five of the last seven presidents, presented with a similar chance to influence the choice of a party nominee, would have waded in, delighting in the opportunity to get even and regain the limelight. Lyndon B. Johnson (who lived by the shiv), Richard M. Nixon (the trickster), Gerald R. Ford (wilier than his Wolverine reputation), Jimmy Carter (not so saintly after all) and Bill Clinton (winning is everything) would have done it. Ronald Reagan and George H.W. Bush, believing that silence in such matters was eloquence, would not.

The voters still have a lot to say. Before it is over, Mr. Gore may have something to say as well.