Romney, in a 1994 Senate race, said he would "protect a woman's right to choose," though he now said he had an epiphany about the issue in 2005 that makes him now oppose abortion rights.
McCain has consistently voted against abortion rights, but his support for embryonic stem cell research and campaign finance reform, which threatened various advocacy groups including those opposing abortion, has alienated abortion opponents.
Thompson's as-yet-undeclared presidential campaign has been something of an anticlimax. After predictions of $5 million in fundraising, his presidential exploratory committee raised $3.5 million after launching in June.
There has also been a great deal of staff turnover at his committee, with some former staffers complaining that his wife, Jeri Thompson, has exerted too much control. The formal campaign announcement, which originally was supposed to be around the Fourth of July, has been pushed off several times.
Many conservative supporters of Thompson see these issues as nitpicking. In one of his many acting roles, Thompson played the president in a TV movie about loose nukes called "Last Best Chance" -- and to many social conservatives, that's what Thompson is himself.