The war is over. Let battle commence. Eight months before the first primary contest, a year before the party national conventions, and 17 months before the first voter casts the first ballot in the next presidential election, the Republican faithful last weekend embraced Governor George W Bush of Texas as the man most likely to reunite their party and recapture the White House from Bill Clinton's Democrats in 2000.

This week Al Gore, the man most likely to defend the White House for the Democrats, was expected to travel home to Carthage, Tennessee, to announce his presidential bid, followed by a week of intense campaigning. The 2000 presidential election is firmly under way.

It may never be as good as this again for Governor Bush as, fortified by a prodigious campaign war-chest and a commanding lead in the opinion polls, he launched his presidential bid in a much-anticipated swing through Iowa and New Hampshire - the two states that will be the first to make their choices in the primaries next spring.

The Republican frontrunner was greeted at each stop by forests of placards, but in many places his supporters were outnumbered by the media army that constitutes one of his campaign's even greater advantages. Between his Iowa and New Hampshire visits Bush paused for a private family reunion with his ex-president father in Kennibunkport, Maine, confident that the attendant snappers would help to strengthen his command of the headlines. One curious effect of the governor's campaign is that his father's reputation is being favourably re-evaluated.

Watching George W Bush, it was hard to remember that the United States is barely at the overture stage of the 2000 presidential race. With Bush accompanied by more than 200 journalists, the hothouse political atmosphere was more appropriate to the closing stages of the contest than to the pre-preliminaries. The contest, though, is far from over.

Until he started his campaign, Bush had maintained two fictions: that he was only considering the possibility of a challenge for the job that his father, George Bush, held from 1989-93, and that he was pre-occupied with the political affairs of Texas, where he was re-elected as governor for a four-year term last November.

In Iowa all such dissembling disappeared. Bush was clearly enjoying every moment of his new-found freedom as he told an audience of Iowa Republicans at the gloriously named World Pork Expo in Des Moines: "Today I announce loud and clear, I'm running for president of the United States." And he added, "I am running to win."

In his first campaign speeches Bush set out some of the broad themes that he hopes will reunite his party - which is deeply divided between moderate and rightwing conservatives - and challenge the post-Clinton Democratic party.

Bush said: "I will not use my office as a mirror to reflect public opinion. I will be guided by conservative principles." He offered a traditional Republican platform of federal tax cuts, increased military spending and social security privatisation. He also promised a reform of tort law to protect business from civil litigation, and committed himself to free trade, which some party rivals oppose.

But Bush also mounted a strong defence of the "compassionate conservatism" that has formed the basis of his strong electoral performances in Texas. Promising to be "a president who sets a tone", he said compassion was "a noble goal" that most Americans would embrace. Pledging to "rally the armies of compassion", he promised: "On this ground I will take my stand."

He was conspicuously silent on the so-called "wedge issues" on which Gore's campaign will concentrate its fire. He said nothing about abortion, gun control laws, or reform of the political campaign finance laws. He also avoided comment on the Kosovo situation.

It was a Panglossian mixture of strictness and flexibility, dogma and decency. The question is whether it will work as successfully on the national stage as it has done in Texas. In the past two presidential elections the Republican nominee has been crippled by his own party. Bush has to find a way of running the same campaign to win the nomination and then to win the election.

It isn't as easy as it looks, even with the lead Bush enjoys over his Republican rivals and Gore, and there are battles still to come. Last weekend, though, those conflicts seemed far off. Most Iowa Republicans are more than ready to anoint a man who is relatively inexperienced, but who carries a formidable pedigree and has made the party feel electable again.

"He's got to come down off Olympus and show he's a real person," warned Dennis Goldford, a professor of political science at Drake university. "People think he'll win, but now he has got to develop his true believers, fire up the organisation."

For all the hype, Bush's campaign is likely to face some severe challenges rather than sweep inexorably to the convention and the White House. In the first place the Democrats speak for the mood of the US more accurately than Bush does: they got Kosovo right, they have got gun control right, and they have got the economy right. Second, the Republican party is a bear garden.

Against that, there is an almost tangible sense that Clinton has exhausted the patience of many Americans. Gore is suffering from the US's post-impeachment tristesse with the Clintons. He will have to struggle to make his voice heard against the echoes of his boss's past.

Nevertheless a week in which the Russian army spectacularly took the US military, intelligence and political establishment by surprise in Kosovo is a good one in which to remember the importance of the unforeseen, and to observe that 17 months is a long time in politics. Remember President Muskie? President Hart? President Glenn? They all looked as hard to beat around now as Bush does today.