Hillary Clinton and Barack Obama struck a rare note of civility in their White House battle, uniting to observe that history was in the air as the Democrats vie to seize back the presidency.

A star-studded audience at the Kodak Theatre — home of the Oscars — was on hand late Thursday for their first one-on-one debate, but the drama and backbiting seen in previous encounters was replaced by a polite exchange of policy priorities.

Elsewhere, California governor Arnold Schwarzenegger endorsed Arizona Senator John McCain, giving the Republican front-runner another key boost before the upcoming “Super Tuesday” battles in 22 states.

Clinton said that while she and Obama may differ on healthcare, economic remedies and how to handle unsavory foreign regimes, what united them was far greater — a shared desire to boot the Republicans out of the White House.

“Just by looking at us, you can tell we are not more of the same,” she said, noting the extraordinary prospect of the first African-American, or first woman, becoming commander-in-chief of the world’s sole superpower.

Illinois Senator Obama — emphasizing his campaign theme of breaking with the old order of politics — described the election as a choice between “the past and the future.”

Hillary Clinton, the wife of former president Bill Clinton, returned to her theme of experience — indirectly highlighting Obama’s perceived lack of it.

She said that on inauguration day next January 20, either she or Obama would be sworn in as the successor to President George W. Bush.

“And then, when the celebrations are over, the next president will walk into the Oval Office, and waiting there will be a stack of problems, problems inherited from a failed administration,” she said, citing Iraq and the economy.

In front of a packed audience that included entertainment industry icons ranging from Steven Spielberg to Stevie Wonder, Obama and Clinton went head to head for the first time since John Edwards quit the Democratic race Wednesday.

Both took pains to praise Edwards — mindful that his supporters are searching for a new candidate — and one another.

“I was friends with Hillary Clinton before we started this campaign, I will be friends with Hillary Clinton after this campaign is over,” Obama said to warm applause.

The issue of judgment provoked one of the rare flashpoints, with Obama once again drawing attention to Clinton’s 2002 vote to support Bush’s use of military force in Iraq.

“Senator Clinton has claimed, fairly, she’s got the experience on day one. And part of the argument that I’m making in this campaign is that, it is important to be right on day one,” Obama said.

Clinton took aim at Obama’s stated intention to seek talks with traditional foes of the United States, most notably Iran.

But the overwhelming tone was conciliatory, with Obama pulling out Clinton’s chair for her after the debate ended, and the two warmly congratulating one other.

Obama did not even rule out the possibility of a “dream ticket” involving the two — as long as he would be top dog.

Talk of prospective running mates was “premature,” Obama said, but acknowledged that Clinton “would be on anybody’s shortlist.”

With more than 2,500 delegates up for grabs on both the Republican and Democratic sides on February 5, the campaigns are all going into over-drive.

The Democratic race has now been transformed into a straight fight between Obama, 46, and Clinton, 60, and all eyes are on Super Tuesday.

In a boost for Obama, campaign organizers said the Illinois senator had raked in a record-breaking 32 million dollars in funds in January alone.

But a spokesman for Clinton dismissed the figures, saying what counted was the New York senator’s proven success in diverse states like New Hampshire, Nevada and Florida.

“Fundraising is one of the most important markers in the lead-up to voting. But once people start voting, that’s a more important measure of a campaign’s success,” Jay Carson said.

Both Obama and Clinton also have to look beyond the primaries to their possible Republican opponent in the November election, with Vietnam war hero McCain now favored to earn his party’s nomination.

Schwarzenegger’s high-profile backing for McCain came after former New York mayor Rudolph Giuliani quit the race late Wednesday and threw his own support behind the Arizona senator, a fellow hawk on national-security matters.

Former Massachusetts governor Mitt Romney is still promising to give McCain a run for his money, and the two clashed repeatedly Wednesday in a heated debate at the Reagan Presidential Library outside Los Angeles.