If ever there was any doubt that Al Gore has lost his mooring since his unsuccessful presidential bid in 2000, he gave proof this week by endorsing Howard Dean for the Democratic presidential nomination. Traveling to Harlem, where he joined Dean at a fundraising event, Gore said he had come to the conclusion that "in a field of great candidates, one candidate clearly now stands out. So I am asking all of you to join in this great movement to elect Howard Dean president of the United States."

Never mind that one of the other "great candidates" is his former running mate, Senator Joe Lieberman. Always a gentleman, Lieberman must be particularly stung by the rebuke, since he waited to announce his own run for president until Gore made it clear that he was not a candidate. To Joe Lieberman, anyway, loyalty counts, but apparently not to the new Al Gore.

And it wasn't just Lieberman that Gore dissed by endorsing Dean. Dick Gephardt -- a sometimes rival who ran against Gore in the presidential primaries in 1988 -- endorsed Gore over Bill Bradley in the early 2000 primaries. At the time, Gore was by no means the sure winner, and he desperately needed Gephardt's support. But Gore wouldn't even maintain neutrality in the crowded 2004 field, much less return Gephardt's favor.

Most puzzling in Gore's endorsement is the wide gulf that exists between Gore's political record and Howard Dean's.

Al Gore was one of the founding members of the centrist Democratic Leadership Council, a group formed to try to reverse the leftward drift of the Democratic Party. As a member of the House of Representatives from Tennessee, Al Gore supported restrictions on abortion and gun owner rights, and made a name for himself as one of the Party's few hawks on national defense. Although Gore later abandoned his pro-life, pro-gun stance, he maintained his centrist position on foreign policy and defense issues.

Dean, on the other hand, has fashioned his entire presidential campaign as the darling of the Left. Dean says he doesn't want to talk about "guns, God and gays," no doubt because those issues have proved losers for Democrats in national elections. But with the exception of gun control -- which he thinks is fine for New York City and Detroit, but not for Vermont -- Dean embraces every plank in the left-wing's agenda.

It's possible that Al Gore has simply reinvented himself so many times that he doesn't know what he believes anymore, so why not jump on the Dean bandwagon, even if it's headed left?

But I think there's a more Machiavellian explanation. Gore wants Dean to win the Democratic nomination in 2004 because he knows Dean will lose to George W. Bush, and that leaves open the possibility that Gore would have a shot at becoming president in 2008.

Of course, Gore would have to beat out Hillary Clinton to win the 2008 nomination, and there's little doubt she will run. In fact, Hillary's performance on the Sunday talk shows this past weekend may be what drove Gore into the Dean camp.

In every recent public opinion poll in which her name has been included among potential Democratic presidential candidates, Hillary runs away with the nomination. She says she's not running in 2004 -- although she refused Sunday to declare she would not accept the nomination if drafted.

But 2008 is an entirely different matter. Both her performance on the Sunday shows -- displaying a command of foreign policy issues, an area that could be problematic for a female candidate -- and her overwhelming popularity among the Democratic faithful jeopardizes Gore's own ambitions. Maybe Gore's calculation is that the sooner Dean emerges as the party's nominee, the quicker Hillary will disappear from center stage.

Whatever his reasons, principle clearly played no role in Gore's endorsement. Gore's willingness to abandon principle when it interferes with his own ambition, however, will come back to haunt him in 2008. Gore's latest reinvention of his persona is the least attractive yet.