A Missouri congressman's startling remarks about "legitimate rape" and pregnancy have set off a torrent of criticism from his fellow Republicans as well as from Democrats. And the episode has made the abortion issue an unwelcome focus for GOP candidates nationwide.

Key leaders in the Republican Party, including presidential candidate Mitt Romney, are urging Rep. Todd Akin to surrender the Republican nomination for the Missouri Senate seat now held by Claire McCaskill, a Democrat who until now has been looking very vulnerable. As of Tuesday afternoon, Akin was holding fast to the nomination, despite backlash from party members and the irritating distraction for the top of the ticket.

Some political and religious spokespeople were expressing support for Akin. The Washington Post also pointed out that others in the past have embraced Akin's assertion that the trauma of rape can block pregnancy.

By now, Akin's words — since disavowed — are etched in the public consciousness: "If it's a legitimate rape, the female body has ways to try to shut that whole thing down," Akin, who opposes abortion in all cases, said Sunday while interviewed on a St. Louis television station. The congressman later apologized, saying he "misspoke" and that "rape is never legitimate."

The GOP party platform, which is staunchly pro-life, has not come out in favor of an abortion exemption in cases of rape or incest. Neither the 2004 nor 2008 platforms included such exceptions. News reports state that language of the 2012 platform, heading to a vote next week at the Republican National Convention in Tampa, will similarly stay silent on these circumstances.

What these platforms do include is support for a "human life amendment" to the Constitution that would bestow variously defined legal rights on human embryos.

(In contrast, the Democratic Party has expressed a firmer pro-choice stance in recent years, stating in 2008 that it "strongly and unequivocally supports Roe v. Wade and a woman's right to choose a safe and legal abortion" while in 2004, it stated that abortion "should be safe, legal, and rare.")

Across the board, Republicans are divided over abortion exemptions for rape, incest or to save the life of the mother, with most remaining either unconditionally opposed or supporting an exception only when the mother's life is threatened.

Broader GOP support for the no-exception rule, in any case, is not unusual: the Texas Tribune reports that state officials from Gov. Rick Perry to Attorney General Greg Abbott only support abortion when it endangers the health of the mother. However, 2008 Republican presidential nominee John McCain had long supported such exceptions, according to the New York Times.

Romney has a more complex history with such exceptions — and abortion in general. Pro-choice in the early days of his political career, Romney switched his position to pro-life in late 2004, while still governor of Massachusetts.

In July 2005, then-Gov. Romney vetoed a bill to make emergency contraception — including the so-called morning-after pill — available over the counter and require that hospitals offer it to rape victims. In an op-ed in the Boston Globe, Romney explained that he believed the drug could terminate life after conception and reaffirmed his anti-abortion position. He also said, however, "I believe that abortion is the wrong choice except in cases of incest, rape, and to save the life of the mother." In any case, his veto was overturned by the Massachusetts Legislature.

By December 2005, shortly before the contraception law was to take effect, Romney ordered even Catholic hospitals to provide the morning-after pill to rape victims. In remarks to the Globe, he said, "My personal view, in my heart of hearts, is that people who are subject to rape should have the option of having emergency contraception or emergency contraception information."

Despite a 2012 Obama ad that claims Romney favors legislation banning abortion in all cases, Romney has publicly restated his support for abortion exemptions as recently as last year.

Following Rep. Akin's controversial remarks, a Romney spokeswoman released a statement Sunday night affirming that "a Romney-Ryan administration would not oppose abortion in instances of rape." By Monday morning, candidate Romney issued a personal rebuke, telling National Review Online that Akin's comments were "insulting, inexcusable, and, frankly, wrong."

While Romney's own views on abortion have been consistent for the last seven years, his selection of Rep. Paul Ryan as his running mate could muddle the picture. Ryan's views on abortion are much narrower, as news outlets have documented. While running for his congressional seat in Wisconsin, Ryan said he opposed abortions in all cases except to save the life of the mother, according to a 1998 profile by the Milwaukee Journal-Sentinel.

"I'm as pro-life as a person gets," Ryan told the Weekly Standard in July 2010.

Last year, Ryan, with Akin, was one of 64 co-sponsors of the "Sanctity of Human Life Act," also known as the Personhood Amendment, which designates the start of human life at fertilization and includes no explicit exemptions for abortion, even for health of the mother. He was also a co-sponsor, along with Akin, of the "No Taxpayer Funding for Abortion Act," which once included a controversial measure limiting Medicaid funding for abortions to "forcible rape," that narrowed the definition to exclude statutory rape and other circumstances.