Republican White House contenders offered a strong show of support for the military mission in Iraq during their first debate on Thursday (May 3) and said U.S. troops should not come home until the war was won. In the early stages of a 90-minute debate at the presidential library of conservative Republican hero Ronald Reagan in the city of Simi Valley, most of the 10 Republican candidates in the 2008 race rallied around the war effort led by President George W. Bush. "We must win in Iraq. If we withdraw, there will be chaos, there will be genocide and they will follow us home," said Arizona Sen. John McCain, who has led the charge in support of the war and backs Bush's plan to increase troop levels in Iraq. On Iran, Rudolph Giuliani, the former mayor of New York and the leader of the Republican pack in national polls, said he was terrified at the thought of Iran acquiring nuclear weapons. "The reality is the use of military force against Iran would be very dangerous," said Giuliani. "It would be very provocative. The only thing worse would be Iran being a nuclear power. It's the worst nightmare of the Cold War, isn't it? The nuclear weapons in the hands of an irrational person, an irrational force." The debate in California comes amid a dour political climate for Republicans six months after the party was tossed from power in Congress. Polls show broad public dissatisfaction with Bush, the Iraq war and Republicans in general. Former Massachusetts Governor Mitt Romney, whose strong fund-raising and establishment support have elevated him into the top tier even though he lingers in single digits in national polls, was pressed for why he changed from being a pro-choice proponent to being a pro-life candidate. "I've always been personally pro-life," he said. "For me it was a great question about whether or not government should intrude in that decision. And when I ran for office I said I'd protect the law as it was which is effectively a pro-choice position. About two years ago when we were studying cloning in our state, I said look, we have gone too far. It's a brave new world mentality that Roe v. Wade has given us, and it changed my mind." Also participating were Kansas Sen. Sam Brownback, Reps. Tom Tancredo of Colorado, Ron Paul of Texas and Duncan Hunter of California, and three former governors -- Mike Huckabee of Arkansas, James Gilmore of Virginia and Tommy Thompson of Wisconsin. The Republican presidential field has sparked some dissatisfaction among activists, particularly conservatives, and two well-known Republicans are waiting to decide whether to jump in the race. Former House Speaker Newt Gingrich says he will make a decision in September. Fred Thompson, a former actor turned senator who went back to acting, is expected to decide by early summer. Thompson, however, is giving his first big political speech on Friday (May 4) night to a conservative group in nearby Orange County, south of Los Angeles. Nebraska Sen. Chuck Hagel, a critic of the war, is also pondering a White House bid. was/mu/