Now the real battle is on and it's going to be hard-fought, writes Conor O'Clery, North America Editor/
Two months ago Terry McAuliffe, chairman of the Democratic Party, told me that the primary calendar was designed to produce a candidate by March 2nd, much earlier than in previous years.
This is precisely what happened. On Tuesday Senator John Kerry emerged as the undisputed Democratic nominee. The primary contests are over and he now goes mano-a-mano with George Bush.
But is the Massachusetts senator fully primed for the eight-month fight, which starts today with the first Bush campaign ads seeking to define Mr Kerry in the most unfavourable light? Up to now the president has stayed presidential, keeping himself above the fray as the Democrats fought it out. On Tuesday evening Mr Bush called Mr Kerry to congratulate him on the nomination and they spoke about having a "great debate" about the issues facing the US.
But from now on it will no longer be "Mr Nice Guy".
The advantage of a candidate emerging early in the process is that he has time to replace exhausted campaign funds.
Mr McAuliffe has set aside $5 million of Democratic National Committee money so that Mr Kerry at least does not find himself as strapped for cash as Bob Dole did after he won the Republican nomination in 1996 - when he couldn't afford the air fare across the country.
The Massachusetts senator will now embark on an intensive series of fund-raisers in the coming weeks to try to match Mr Bush's overflowing war chest. He chose not to claim matching federal funds so he is not bound by spending limits, and advocacy groups like Moveon.org, which has backing from billionaire George Soros, are preparing to shell out millions of dollars in an anti-Bush advertising campaign. Money might not be such a big problem.
The disadvantage of an early end to the primary contests is that the winner has not been battle-tested as much as he would have been in a longer season. Little blood was left on the floor in the Democratic debates, and Mr Kerry showed irritability when taken to task fairly gently by John Edwards over trade issues in the final weeks.
His credibility has been barely challenged and Republicans will try to tear it to shreds.
He supported the war in Iraq, for example, but then compromised as Howard Dean surged, and he enthusiastically backed NAFTA (North American Free Trade Agreement) in the past but accommodated himself to the populist protectionism that gave John Edwards a big boost in Wisconsin. His record in the Senate is also one of a law-maker who accepted more special interest funds than anyone else.
Such questions did not bother Democratic voters much in the primaries.
Exit polls on Tuesday showed that Mr Kerry has wide appeal with every category of Democrat across the United States - rich and poor, black and white, Catholic and Protestant, union members and business owners, and urban, suburban and rural dwellers. They are united in a ferocious determination to get rid of Mr Bush.
Mr Kerry's most important quality, voters said, was his potential to beat George Bush. In New York four out of five voters who said they were looking for a candidate to beat Mr Bush opted for Mr Kerry rather than any other Democrat.
Now that they have got him, the real political struggle is on. How Mr Kerry identifies himself to the independents and the swing voters in crucial states like Ohio, Florida, West Virginia, Pennsylvania and Wisconsin will influence the outcome. The three-term senator has not yet won over independents, according to the exit polls, and has yet to make an impression outside Democratic ranks.
In the Georgia primary more independents voted for Mr Edwards than Mr Kerry.
A fascinating aspect of the coming contest is that Mr Kerry stands for everything Mr Bush has rejected. One fought in Vietnam, the other avoided combat. Both are Yale graduates with north-eastern Brahmin origins but the Bush family transplanted itself to oil-rich Texas and the president has cultivated an image of hard-scrabble God-fearing southern cowboy, which has more appeal to Republican grassroots than that of an elitist Massachusetts liberal.
Kerry counters his privileged background by telling rallies that he has devoted himself to a lifetime of fighting for less-privileged people. His big challenge is to distance himself from the liberal stereotype which haunted Michael Dukakis, the last Massachusetts native to get the Democratic nomination and who failed spectacularly to beat the Republican George H.W. Bush in the presidential election of 1988.
The issues, according to the exit polls, are overwhelmingly the economy and jobs, followed by terrorism and Iraq. Mr Bush has to overcome the perception that the economic recovery has done nothing for job growth. The president has a big credibility problem with the failure to find weapons of mass destruction, the mess in Iraq, understatements of budget estimates and overestimations of new jobs and a runaway deficit.
Having got a candidate with the gravitas, stature and a war record to take on Mr Bush, Democrats will now try to make the election a referendum on the president. With core party members that's the one and only issue. Theirs is the oldest catch-cry in American politics - "throw the bum out".
For the past two months, as the Democrats dominated the media, Mr Bush has seemed defensive, and at times overwhelmed, by the problems he faces. He failed to impress in his State of the Union message. He is trailing Mr Kerry in the polls. He has often been underestimated as a political fighter and has the benefit of incumbency and pots of money to make his case. However, Mr Kerry also has a reputation as a "good closer", someone who gets fully engaged near the end. And this fight is only starting. It's going to be dirty, knock-down, vicious - and endlessly fascinating.