Potential Democratic presidential candidates who voted to give President Bush the authority to use force in Iraq could face a political problem -- they supported a war that their party's rank-and-file now strongly view as a mistake.

Their pro-war votes -- cast three years ago -- could haunt them as they seek early support among die-hard Democrats and gauge whether to launch formal candidacies for the party's 2008 presidential nomination.

"For a lot of activists, this could be a threshold issue. They may be looking for somebody without any taint for prior support for the war," said John J. Pitney, a political science professor at Claremont McKenna College in California.

Sens. Evan Bayh (search) of Indiana, Joseph Biden (search) of Delaware, Hillary Rodham Clinton (search) of New York, John Kerry (search) of Massachusetts and former Sen. John Edwards (search) of North Carolina are mulling over running for the Democratic nomination. All voted in October 2002 for a resolution authorizing the president to use force in Iraq.

They no doubt will be forced to explain their positions — both then and now — and in doing so could open themselves to attack from candidates who didn't support the resolution or didn't have to cast the politically tricky vote.

The only other oft-mentioned potential Democratic presidential candidate in the Senate — Russell Feingold (search), D-Wis. — voted against the resolution. Other possible hopefuls, such as Govs. Mark Warner (search) of Virginia, Bill Richardson (search) of New Mexico and Tom Vilsack (search) of Iowa, weren't in Congress.

Primary races are all about which candidate gets the largest share of support from the party faithful. Public opinion polls show that Democratic loyalists overwhelmingly disapprove of Bush's handling of the war and believe the United States should never have gone into Iraq in the first place.

That staunch opposition raises questions of whether Democratic primary voters will be comfortable supporting a candidate who at least initially backed the war they oppose.

The situation facing Democrats who voted for the Iraq war resolution has been likened to Sen. Eugene McCarthy's 1964 vote in favor of the Gulf of Tonkin (search) resolution, perceived as the vehicle that gave President Johnson carte blanche to escalate the Vietnam War.

McCarthy, D-Minn., had become a war critic by the time he announced his intention to challenge Johnson for the Democratic nomination in 1968. But McCarthy didn't pay a political price for his Gulf of Tonkin vote.

In fact, McCarthy was such a vehement foe of the war that he was on the razor's edge of the opposition. That contributed to Johnson's decision not to seek another term.

The race for the 2004 Democratic nomination produced conflicting lessons about how support for the Iraq war could affect a candidacy.

Two months before the Iowa caucuses, polls showed Rep. Dick Gephardt, D-Mo., vying for the lead in a crowded Democratic field.

Then, former Vermont Gov. Howard Dean launched a TV ad in Iowa criticizing Gephardt's work with the Bush administration in drafting the Iraq resolution. It showed Gephardt, then the House minority leader, standing alongside Bush in the White House Rose Garden.

The ad has been credited with helping to sink his candidacy.

Even so, Dean's anti-war candidacy flamed out after being the early favorite. And Democratic voters ended up looking past Kerry's support of the resolution when they chose him as the party's nominee.

Democratic strategists point to that as they play down the possible impact of the Iraq resolution vote on the 2008 Democratic race.

They note that the primary season is more than two years away. Voters likely will focus on the candidate's current positions on Iraq, a plan for withdrawing U.S. troops, and a future vision for the military and its veterans, they say.

Democrats, strategists say, likely will mull questions such as: Did candidates who voted initially for the war continue voting to give the president billions of dollars to continue operations? Did they press for a withdrawal strategy? What was their position as the war dragged on with no end in sight, casualties climbed and the price tag soared?

"It's going to be about what did you do since you voted for the war," said Celinda Lake, a Democratic pollster.

Still, Donna Brazile, Al Gore's 2000 campaign manager, said discussions of how candidates voted on the Iraq war resolution vote will occur as potential candidates rally supporters and try to raise money early on.

"This could be an issue -- but one of many issues," Brazile said.