It felt more like a religious revival meeting. In spite of being introduced as the "First Lady of Television", Oprah Winfrey could as easily have been described as the preacher-in-chief. Endorsing Barack Obama as "the one, the one I have been waiting for", Ms Winfrey played the unlikely role of John the Baptist to Mr Obama's Jesus.
Addressing a boisterous crowd of 8,000 who had queued outside for more than an hour in the freezing cold, Ms Winfrey did not once by name mention Hillary Clinton, who remains the Democratic frontrunner. Nor did Mr Obama. But the combined message was more than clear: Mrs Clinton lacks the moral rectitude to lead the US. Only Mr Obama possesses that.
"It is your time to seize the opportunity to support a man who, as the Bible says, loves mercy and does justly," the television celebrity told the packed indoor stadium. "We need a president who has a conscience and who knows how to consult his conscience so that he can proceed with moral authority. It isn't enough to tell the truth - we need politicians who know how to be the truth."
With just 23 days remaining before the critical first presidential nominating caucus in Iowa and 28 days before the first primary in New Hampshire, Ms Winfrey's intervention was perfectly timed from Mr Obama's point of view.
Polls show the first-term senator running neck and neck with Mrs Clinton in Iowa and running a close second to her in New Hampshire and South Carolina, which holds the second primary in late January and where Ms Winfrey and Mr Obama attracted a crowd of 29,000 at a rally earlier on Sunday.
Election analysts say it is too soon to tell whether Ms Winfrey's intervention will provide a significant boost to Mr Obama's campaign or whether - as has tended to be the case with presidential celebrity endorsements - it merely attracts crowds rather than votes. However, Ms Winfrey is no ordinary celebrity. And Mr Obama's campaign is built on the premise that he is no ordinary politician.
In contrast to Mrs Clinton's stump speech, which is replete with policy detail and which emphasises her "strength and experience", Mr Obama's standard address is about "changing the way we do business in Washington". It emphasises his "unique" outsider credentials to push that through.
Following on from Ms Winfrey, who concluded: "I'm sick of politics as usual. We need Barack Obama," the first term senator from Illinois picked up on the TV host's semi-biblical theme. Quoting Martin Luther King, Mr Obama urged voters to seize the "fierce urgency of now".
He said: "I give praise and honour to God. Look at the day the Lord has made."
Whichever candidate Democratic voters nominate eventually, Mr Obama's well-timed ascendancy is beginning to attract notice among the leading conservative organs, most of which had until recently assumed that Mrs Clinton's nomination was all but inevitable.
In a foretaste of how a general election might play out were Mr Obama the Democratic nominee, he is described as "Saint Obama" on the cover of the latest issue of the neoconservative Weekly Standard. Likewise, Mr Obama graces the cover of this month's National Review, which likens his campaign to that of Jimmy Carter, whose outsider status appealed to Americans after the squalor of the Nixon years.
Mr Carter is also remembered as the most preachy of US presidents. "All presidential candidates think highly of themselves," says the article. "The personal messianism of a Carter or an Obama, though sets them up [for an] undoing."