Jan. 31 (Bloomberg) -- Republican John McCain and chief rival Mitt Romney clashed over immigration, taxes, climate change and the Iraq war in their last scheduled debate before a round of voting Feb. 5 that may settle the party's presidential nomination race.

McCain entered the forum at the Ronald Reagan Presidential Library in California as the front-runner after having won Florida's primary this week and getting the endorsement of former New York Mayor Rudy Giuliani. He will be endorsed today by Governor Arnold Schwarzenegger of California, the state that is the biggest prize in next week's primaries and caucuses.

Romney set the tone at the opening by attacking McCain for having cooperated with Democrats on immigration and climate change, saying he demonstrated views ``outside the mainstream of Republican conservative thought.'' He also said McCain's endorsement by the New York Times means ``you're probably not a conservative.''

McCain hit back.

``Let me note that I was endorsed by your two hometown newspapers who know you best, including the very conservative Boston Herald,'' the Arizona senator replied. ``I'll guarantee the Arizona Republic will be endorsing me, my friend.''

Analysts said sometimes acrimonious exchanges between McCain and Romney would do little to alter the trajectory of campaign.

``Not too many votes are going to be changed,'' said John J. Pitney, a political science professor at Claremont McKenna College in California. ``All the candidates are in a well-worn groove.''

Four Candidates

Along with McCain and Romney, the former governor of Massachusetts, the debate included former Arkansas governor Mike Huckabee and Ron Paul, a U.S. House member from Texas.

The focus on the two leaders prompted Huckabee to plead for more time.

``I want to make sure everybody understands, this isn't a two-man race,'' he said.

The first portion of the forum, sponsored by the Los Angeles Times, Politico and CNN, focused on the economy.

McCain praised the Bush administration's handling of the subprime crisis, saying its root cause was loose credit and greed on Wall Street.

``I think there are some greedy people on Wall Street that perhaps need to be punished,'' McCain, 71, said.

`Squeezed' by Economy

Romney said middle-income families are ``feeling squeezed'' by the housing crisis and rising energy prices.

``And as a result, we've got people that feel there needs to be a change in Washington, and that's something I represent,'' Romney, 60, said.

The two men rehashed past arguments over immigration, their commitment to lowering taxes and the way to deal with climate change.

Romney said McCain's support for limits on greenhouse gases would impose a ``huge'' tax on the public and cause energy- intensive industries to flee the country. McCain countered that suggesting that steps to limit emissions would be costly indicates Romney ``does not have confidence in the ability of Americans to address this issue.''

The tension flared again when the debate eventually turned to Iraq, and Romney accused McCain of mischaracterizing his words on the war. McCain insisted that Romney had, at one point, supported a timetable for withdrawing from Iraq.

``I have never, ever supported a specific timetable for exit from Iraq, and it's offensive to me that someone would suggest that I have,'' Romney said.

`Dirty Trick'

He said McCain waited until just before the Florida primary to level the charge, and the timing was ``the kind of dirty trick that I think Ronald Reagan would have found to be reprehensible.''

McCain denied that he was springing a trap on Romney.

``I raised it many times, as to whether you have the experience and the judgment to lead this country in the war against radical Islamic extremism,'' he said. ``I've raised that many times.''

The late former president figured prominently in the debate. Asked which of them Reagan would probably endorse if he were alive today, Romney and McCain jockeyed to position themselves as the embodiments of Reagan's values while using the question to reinforce their criticisms of each other.

Reagan's Legacy

``Ronald Reagan would say, as I do, that Washington is broken,'' Romney said. ``And like Ronald Reagan, I'd go to Washington as an outsider -- not owing favors, not lobbyists on every elbow. I would be able to be the independent outsider that Ronald Reagan was.''

Responded McCain: ``Ronald Reagan would not approve of someone who changes their positions depending on what the year is.'' Reagan's legacy, he said, is ``sticking to principle and doing what you believe in, no matter what.''

In a moment of modesty during an evening marked by one- upmanship and rancorous exchanges, Huckabee replied that it would be ``presumptuous and even arrogant for me to try to suggest what Ronald Reagan would do.''

Huckabee, 52, said he hoped Americans hadn't lost the ``Reagan spirit'' that ``brought this country back together and made us believe in ourselves.''

To contact the reporter on this story: Hans Nichols in Simi Valley, California, at hnichols2@bloomberg.net; Indira Lakshmanan in Simi Valley, California, at ilakshmanan@bloomberg.net

Last Updated: January 31, 2008 00:41 EST