Obama starts to punch his weight, leaving Hillary on the defensive

The race for the Democratic nomination in the 2008 presidential election took a dramatic turn in Iowa this weekend when Barack Obama put in an electrifying performance that left rival candidates' campaigns – including Hillary Clinton's – stunned and momentarily silenced.

In virtually every state except Iowa, Mrs Clinton holds a commanding lead over her rivals at the polls. But her coronation as the Democratic candidate – which some sections of the media say is inevitable – is no sure thing in Iowa. Mrs Clinton's steamroller of a campaign could come to a juddering halt as early as 3 January, when the flinty voters of America's corn belt cast a cold eye over the candidates and make up their own minds. In living rooms, school houses and town halls across the state, Democrats will gather to "caucus," and make the first real choices in the 2008 race for the White House. For the three leading candidates, Mrs Clinton, Mr Obama and John Edwards, Iowa may be decisive. And a victory for Mr Obama, which on the basis of the reception he received on Saturday night must be a real possibility, would be a major setback for an already rattled Clinton campaign.

On the evidence of Saturday night, when each candidate stepped into a boxing ring converted into a stage, in the middle of a noisy sports arena, it was Mr Obama who stole the evening.

For Democrats, disenchanted with his non-confrontational style of electioneering, this was the moment he put on the boxing gloves. Without once mentioning Mrs Clinton's name, he mercilessly pummelled her as a candidate from the past, a creature of opinion polls who approached the election with a dangerous sense of entitlement. Mrs Clinton's campaign, he suggested, was no different from the Republicans' and focused only on winning the White House.

"I don't want to spend the next year or the next four years refighting the same fights that we had in the 1990s," he said. "I don't want to pit red America against blue America – I want to be the president of the United States of America."

Focusing laser-like on the opportunism he says was behind Mrs Clinton's support for the war in Iraq, he said: "When I am your nominee, my opponent won't be able to say I supported this war in Iraq, or that I gave George Bush the benefit of the doubt on Iran. And he won't be able to say I wavered on something as fundamental as whether it's OK for America to use torture - because it's never OK."

For an audience that had waited in the cold for hours, while Democratic grandees were served dinner, Mr Obama's speech was a barnstorming climax to a six-hour marathon.

To thunderous applause from supporters who outnumbered those of all other candidates, he denounced the presidency of George Bush, the war in Iraq and the grave danger of another disastrous military adventure in Iran. Then, his voice momentarily cracking, he invoked the name Martin Luther King to justify his run for President – when so many had counselled him to wait his turn.

"I'm running because of what Dr King called "the fierce urgency of now," he explained. "I'm running because I believe there's such a thing as being too late. And that hour is almost upon us." Mrs Clinton, who spoke before him and was nursing a cold, delivered a speech that her advisers said afterwards was pitch perfect.

She focused on redirecting the audience's attention away from herself to the Republicans. Her famously disciplined campaign had earlier handed her supporters new canary yellow T-shirts emblazoned with "turn up the heat". It was a phrase Mrs Clinton repeatedly used, in an otherwise stock speech peppered with homilies in which her denunciations of the Bush White House were followed by a full-throated roar from her supporters to "turn up the heat".

"When the Republicans turn over our energy policy to the oil companies and deny global warming what do we do?" she asked.

"Turn up the heat!" they responded, prepped by years of cheerleading for college sports teams.

At heart, she presented herself as the experienced political battler and said Democrats should pick "a nominee who has been tested and elect a president who is ready to lead on day one."

"There are some who will say they don't know where I stand," she said, her voice powerful and soaring. "I think you know better than that. I stand where I have stood for 35 years. I stand with you. And with your children. And with every American who needs a fighter in their corner for a better life."

Away from the din of the sports arena, Democrats in Iowa must now make up their minds. Senior Clinton advisers were dismissive of the enthusiasm for Mr Obama, saying he had bussed in supporters from as far away as Chicago and that they were not real Iowan caucus-goers.

Others dismiss as unlikely that pragmatic rural Iowans, from a farm state that is overwhelmingly white, will support a black candidate for president.

Surprisingly, that may not be the case. When Mrs Clinton addressed the Iowa farm union earlier in the day, she was given a lukewarm reception. "I feel she's being forced down our throat," said Vicki Trytten, an organic dairy farmer.

The remarks of several other farmers who heard Mrs Clinton speak were unprintable. Republican voters in the last two elections, they volunteered that the one candidate they had encountered who had impressed them was Mr Obama. "He acted like he really cared when he addressed us and then stayed back to take our questions individually," said Ron Warren, a farmer. "I like the way he presents himself, I would put him close to John Kennedy."

While the candidates went through their paces in the sports arena, Les Norin, a firefighter and military reservist, was equally antagonistic towards Mrs Clinton: "If I as much as hear Hillary say hello, my hair will go on fire."

As he focuses his energies on swaying more Iowa voters over the next eight weeks, Mr Obama will be hoping his speech brought him another step closer to a famous upset victory two days after New Year.