Bopp emphasizes that other prominent political leaders, such as Ronald Reagan and George Bush Sr., supported abortion rights before converting to anti-abortion positions. "There are millions of people who are pro-life who had abortions -- we know that people can convert."
But a number of prominent conservative leaders such as Paul Weyrich, the Family Research Council's Tony Perkins, and Donald Wildmon are not yet convinced, and some openly doubt the sincerity of Romney's beliefs.
"The last message we want to send to prospective candidates in future elections is to say that you can spend your entire political career trashing the values of social conservatives and then win our support by claiming to have a deathbed conversion just before running for president," said Gary Glenn, a leader of the American Family Association.
"It is my opinion that social conservatives will not be fooled by another liberal Massachusetts flip-flopper who insistently promoted abortion on demand, gun control and the agenda for homosexual rights."
John MacMillan, Republican town committee chairman in Billerica, Mass., supported Romney when he first ran for office as the state's governor in 2003. But he said that he became quickly disillusioned.
"He's as phony as a three-dollar bill," said MacMillan. "When I started to look at his positions -- gun control, pro-gay -- I found out that he's just as bad as [Democratic Sen.Ted] Kennedy. I've been a Republican all my life, and leopards don't change their spots. He'll change his position, say anything, to get votes."
Political historians say that it's not uncommon for candidates to change their positions on the way to higher office -- with varying results.
George Bush Sr. supported the Equal Rights Amendment, abortion rights and described Ronald Reagan's economic policy as "voodoo economics" during the 1980 primary. By the time he became Reagan's vice president, he'd changed his mind on all those positions. Combined with the betrayal of his "read my lips" pledge on taxes, all those switches contributed to the perception that Bush waffled on the issues.
"It seemed that he didn't have a center," said Tim Naftali, the incoming director of the Nixon Library. "Doonesbury made fun of him by portraying him as just a voice, as if to say that he didn't have a core."
Naftali said that other leaders, from Franklin Delano Roosevelt and Reagan to Robert Kennedy, switched their positions on important issues. "The question is, when does the bait and switch happen?" he asked. "It happens when you run on one set of policies and then in office you do something else. If they're going to make the change, I prefer that they do it before they're in office."
Michael McGerr, a political historian at Indiana University, said that Romney's change of views on several important issues is fairly unusual in a political campaign.
"There is always some fudging and blurring on the positions and there are periods of time in which a good number of leading politicians within a party make an adjustment but not individual major contenders," he said. "That's not so common because politicos don't tend to get caught changing their stances on the issues."
Mitt Romney: On the Issues
1994: Believed abortion should be safe and legal
2002: Personally against abortion but pro-abortion rights as governor, endorsed legalization of RU-486 (morning-after pill)
2007: Firmly anti-abortion
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