DURHAM, N.H. – Republican presidential candidates elbowed one another for advantage Wednesday in a debate kicking off a fall sprint to the primaries – and slammed new rival Fred Thompson for skipping it.

They disagreed over illegal immigration, abortion and crime.

But it was the new competition from Thompson, who declared his candidacy Wednesday evening on the Jay Leno program and skipped the debate, that dominated the opening of the 90-minute face-off televised nationally on the Fox News Channel.

“I’d rather be in New Hampshire with these fine people,” said former Arkansas Gov. Mike Huckabee.

“Maybe we’re up past his bedtime,” said Sen. John McCain of Arizona to laughs and some groans from a Republican audience. “The people of New Hampshire expect to see you. They expect to see you a lot.”

“Why the hurry? Why not take some more time off?” joked former Massachusetts

Gov. Mitt Romney, referring to Thompson’s five-month wait before declaring his candidacy.

“This is a nomination you have to earn,” said former New York Mayor Rudy Giuliani.

Even as eight candidates took the stage for their fifth debate of the campaign, they all were aware that they faced not only one another in the more intense, post-Labor Day campaign but also Thompson’s new candidacy.

The campaign enters the fall in flux – with Giuliani leading national polls, Romney leading in the early voting states of Iowa and New Hampshire, Huckabee threatening to move up and Thompson drawing a lot of interest among undecided Republicans.

Thompson skipped the debate, ostensibly because he still wasn’t a candidate when the debate was held, from 9 p.m. to 10:30 p.m. EDT. But he announced his candidacy on the Leno program, taped before the debate, for airing afterward.

He also ran a 30-second television ad during the debate.

“We can’t allow ourselves to become a weaker, less prosperous and more divided nation,” Thompson said in the ad.

His refusal to participate in debate irritated at least some New Hampshire Republicans.

“He seems to be getting off on the wrong foot,” New Hampshire Republican Party chairman Fergus Cullen told McClatchy Newspapers.

Also appearing in the debate at the University of New Hampshire were Sen. Sam Brownback of Kansas, Rep. Duncan Hunter of California, Rep. Ron Paul of Texas and Rep. Tom Tancredo of Colorado.