It is the vote that will not die, no matter how often Sen Hillary Rodham Clinton explains, defends or takes responsibility for her 2002 decision to back the use of military force in Iraq.
And whether it turns out to be a short footnote or a dead weight on Clinton's White House campaign could be the biggest question in the 2008 Democratic presidential race.
Despite pressure from anti-war Democrats, Clinton has refused to apologise for her US Senate vote authorising the use of force in Iraq or call it a mistake.
The mistakes, she says, were committed by President George W Bush.
She tells campaign crowds she would not have cast the vote if she knew then what she knows now.
She says she meant to authorise the return of UN inspectors to Iraq rather than the launch of pre-emptive war.
But while the New York senator and former first lady has become a strong critic of the war and promises to end it if elected, she cannot shake questions about the vote or put the issue behind her.
It flared again on Wednesday, when Hollywood mogul David Geffen criticized her refusal to call the vote a mistake and Democratic rival John Edwards drew a comparison with Bush's reluctance to admit mistakes in Iraq.
<b1>For Clinton's front-running campaign for the Democratic nomination, the biggest unknown is whether voters ultimately question her judgment or credit her resolve.
Is it a classic political calculation or a gutsy stand?
Clinton aides and supporters say the issue is overblown and most voters are looking ahead. But some party strategists say the longer the issue lingers, the more it hurts her.
"The left in our party is not going to give her a pass until she says it was a mistake," Democratic consultant Dane Strother said.
"If she'll just say that, people will hear her say other things as well. But right now no one hears anything other than she won't say her vote was a mistake," he said, adding Clinton's stance plays into her image as a politician who can at times be too calculating.
We want emotion: Democrats
"We don't want calculated on this issue, we want emotion because we are emotional about it," Strother said of Democrats.
Doug Schoen, a White House pollster for former President Bill Clinton, said she had nothing to apologise for given the faulty intelligence offered by the White House before the Iraq invasion.
"You don't apologise when you have been given what appears to be deliberately rigged intelligence," Schoen said, adding poll numbers for Clinton, who leads the Democratic field in national surveys, show no sign of erosion over the issue.
"There is a small cadre of activists who probably weren't with her initially who want her to apologise.
That is a narrow segment of the Democratic Party, it certainly is not broadly representative of the national electorate," Schoen said
The other Democratic White House hopefuls who voted for the Senate authorisation -- Edwards, a former senator from North Carolina, and Sens Chris Dodd of Connecticut and Joseph Biden of Delaware -- have called the vote a mistake.
At a Wednesday forum in Nevada and again in a television interview on Thursday, Edwards said Clinton's stance raised questions about her judgment and prompted comparisons to Bush.
"We've had six-plus years of a president who never acknowledges a mistake unfortunately, and there's been huge negative consequences from that," Edwards said on NBC's "Today" show.
"The real question is, if we make a mistake, do we have a good sense and the judgment and the honesty to admit it and to acknowledge what's happened and to change course," he said.
Clinton's other top-tier rival, Sen. Barack Obama of Illinois, was an early opponent of the war but was not in the Senate at the time of the vote.
Clinton said she would rather lose the support of Democrats concerned about her vote than adopt an approach she is not comfortable with.
"If the most important thing to any of you is choosing someone who did not cast that vote or said his vote was a mistake, then there are others to choose from. But for me, the most important thing now is trying to end this war," she said last weekend in New Hampshire.