Bill Clinton once vowed to fight for voters "until the last dog dies." Tonight he shows how hard he will fight for Democratic presidential hopeful Barack Obama on the Clintons' last big day of the 2008 campaign.
The former president's prime-time speech is the capstone on an eventful day at the Democratic National Convention, which will nominate Mr Obama (47) as the Democrats' candidate to face Republican John McCain in the November 4th election.
After a campaign stop with veterans in Billings, Montana, Mr Obama will arrive in Denver for his speech accepting the nomination tomorrow, when he will wrest attention from the Clintons who have been a huge presence at the four-day convention so far.
Hillary Clinton (60) who lost to Obama in a protracted primary battle but threw herself forcefully behind him in a well-received speech last night, is expected to formally free her delegates to back Mr Obama later today.
"Barack Obama is my candidate. And he must be our president," she said to roars of approval in a speech that left no doubt of her desire to set aside grievances and seek party unity to defeat the Republicans after eight years of President George W. Bush.
Republicans, who have set up an outpost in Denver to hector Democrats, have been trying to exploit any signs of Democratic division. While conceding that Ms Clinton made a strong speech, they reiterated the main thrust of their attack on Mr Obama: that the one-term senator is unprepared to be president.
"It seems to be a very technical speech about being a Democrat, supporting (Obama) as a Democrat, but she never answered the big question (on whether he was ready)," Republican former New York City mayor and unsuccessful presidential candidate Rudy Giuliani told CNN.
In a symbolic gesture, Hillary Clinton will be formally nominated today as a way of honoring her and placating her supporters, some of whom have been complaining loudly that Obama did not pick her as his vice presidential running mate.
Later, delegates will cast their votes for Mr Obama as the party's nominee.
Sign-waving convention-goers, seeking eagerly to win back the White House, also will hear from the man who will likely lead the attack on Mr McCain, Mr Obama's vice presidential running mate, veteran Delaware Senator Joe Biden.
Democrats are honing a message aimed at accusing Mr McCain of being out of touch with everyday American economic concerns at a time of economic malaise in the world's largest economy because he and his wealthy wife, Cindy McCain, own seven homes.
But the event with the most potential for drama will come when Bill Clinton takes the stage.
More so than his wife, Mr Clinton has had trouble reconciling with Mr Obama after a primary feud in which Mr Obama, who would be America's first black president, accused Mr Clinton of injecting racial politics into the campaign.
"There is still work to do on the Bill Clinton front," Howard Wolfson, former Hillary Clinton senior campaign strategist, wrote in The New Republicthis week.
The former president again muddied the waters yesterday with remarks that Republicans seized on that they said questioned whether Mr Obama could be effective.
"Candidate X agrees with you on everything but you don't think that person can deliver on anything. Candidate Y disagrees with you on half the issues but you believe that on the other half the candidate will be able to deliver," the former president said.
Sometimes known in the US media as "the Big Dog," Mr Clinton capped a comeback in his 1992 presidential campaign by promising to fight for New Hampshire voters "until the last dog dies."
Some Democratic delegates at the convention believe that in the end, the Big Dog will bark loudly on behalf of Obama.
"Bill Clinton's feeling are hurt. His ego is bruised," said Brandon Hines, who, at 20, is Michigan's youngest delegate. "I think he will come around for Obama."
The ex-president could be seen tearing up last night as he sat in the audience and applauded as his wife asked her supporters to back Mr Obama.
After running behind Mr Obama in public opinion polls for months, Mr McCain expressed surprise that he had pulled ahead of the Democrat in a Gallup daily tracking poll that had him leading 46 percent to 44 per cent.