Hillary Clinton's supporters gave a fresh glimpse yesterday of their lingering resentment over her defeat by claiming that she would have won the Democratic presidential nomination if John Edwards had confessed his affair earlier.

Howard Wolfson, her former communications director, suggested that the lie Mr Edwards told last year over his adulterous relationship with Rielle Hunter had lasting effects because it enabled him to stay in the race at a crucial time.

The Iowa caucuses, which kicked off the nomination process in January, saw Mrs Clinton finish third, narrowly behind second-placed Mr Edwards and the victorious Barack Obama. Although she staged a comeback a few days later in New Hampshire, her campaign never properly recovered its former poise and momentum.

Mr Wolfson said that without Mr Edwards complicating the contest “we would have won Iowa, and Clinton today would therefore have been the nominee”.

He added: “Our voters and Edwards's voters were the same people. They were older, pro-union. Not all, but maybe two-thirds of them, would have been for us and we would have barely beaten Obama.”

Another leading Clinton campaign backer, James Carville, said: “My instinct tells me that she probably would have done better had Senator Edwards not been on the ballot in Iowa, but that wasn't the circumstances at the time.”

Although Mr Obama's campaign is said to dispute this analysis, pointing out that his biggest harvest of votes came shortly after Mr Edwards dropped out at the end of January, it is in no mood to pick a public fight with the Clinton camp.

Aides are locked in delicate negotiations about whether to have a roll call of delegates at the convention in Denver this month, allowing Mrs Clinton's supporters the chance they crave to put on a show of strength but also reminding voters just how fierce the fight was for the nomination.

Mrs Clinton has been given a prime-time platform for a speech on August 26, the second night of the convention — when she may be introduced by her daughter Chelsea — in an attempt by Mr Obama to make peace with her women voters whose support will be pivotal in November's general election.

Her appearance will coincide with the 88th anniversary of women's suffrage in America and there are plans for two rallies of Clinton supporters in Denver on the same day. Bill Clinton, the former President, who is understood to be angry over the insinuation from the Obama camp that he played racial politics during the primaries, has been given a slot on Wednesday when he risks being overshadowed by a big speech from the vice-presidential nominee. Despite efforts this summer to paper over the cracks between the two campaigns, fresh evidence of them emerged yesterday when the Atlantic magazine published a series of strategy documents drawn up by Mrs Clinton's aides earlier this year.

These include one from Mark Penn, her chief pollster, who wrote: “I cannot imagine America electing a president during a time of war who is not at his centre fundamentally American in his thinking and in his values. Let's explicitly own ‘American' in our programmes, the speeches, and the values. He [Obama] doesn't. His roots to basic American values and culture are at best limited.”

John McCain, the Republican nominee, has also sometimes sought to contrast Mr Obama's exotic background with his own record of military service.

Yesterday, however, he was emphasising his foreign policy expertise with a tough statement on the gathering crisis in Georgia. Some Democrats have privately expressed concern that Mr Obama has left the field free for Mr McCain this week by taking a family holiday in Hawaii.

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