Senior Republicans urged congressman Todd Akin on Monday to quit the U.S. Senate race in Missouri over his inflammatory remarks about rape that distracted from the party's nomination next week of Mitt Romney for U.S. president.
Akin was widely criticized for saying in a television interview Sunday that women have biological defenses to prevent pregnancy in cases of "legitimate rape," making legal abortion unnecessary.
As pressure built on Akin, Republicans cut off cash for his campaign which had looked like a relatively easy victory against Democratic Senator Claire McCaskill.
The furor pushed the campaign debate squarely onto social issues and away from jobs, which Romney has tried to keep at the center of his bid to win the Nov. 6 presidential election.
Akin's remarks complicated Republican efforts to capture the four Democratic seats they need ensure a majority in the 100-member Senate.
U.S. Senator John Cornyn, chairman of the influential committee that raises money for Republican Senate candidates, called Akin's comments "indefensible."
The committee will withhold $5 million in planned spending on TV advertising in Missouri if Akin does not step aside, a committee official said.
"I recognize that this is a difficult time for him, but over the next 24 hours, congressman Akin should carefully consider what is best for him, his family, the Republican Party, and the values that he cares about and has fought for throughout his career in public service," Cornyn said.
Republican National Committee Chairman Reince Priebus, asked whether Akin should drop out of the Senate race, told CNN: "If it was me, I would step aside and let someone else run for that office." Priebus condemned Akin for a "bizarre statement" that is "biologically stupid," and said he would prefer if Akin not attend the Republican National Convention next week.
Democrats used the Akin remarks as evidence that Republicans are waging a "war on women," largely over birth control.
"Rape is rape," Obama said. Akin's comments underscore "why we shouldn't have a bunch of politicians, a majority of whom are men, making health care decisions on behalf of women," he said.
Akin, a Tea Party-backed conservative who opposes abortion, caused an uproar when he said in the interview that the need for abortions in the case of rape was "a particularly tough ethical question."
"It seems to me, from what I understand from doctors, that is really rare," Akin said of pregnancy caused by rape. "If it's a legitimate rape, the female body has ways to try to shut that whole thing down," Akin said.
Romney, who polls show trails Obama with women voters, called Akin's comments "insulting, inexcusable, and, frankly wrong" in an interview with the National Review online.
The controversy took the spotlight away from Republican Party preparations for the coronation of Romney as its nominee at the national convention next week in Tampa.
The firestorm over Akin's remarks erupted as another Republican lawmaker, freshman congressman Kevin Yoder, came under fire for swimming naked in Israel's Sea of Galilee during an August 2011 trip with other members of Congress. Both events featured prominently on the national television news broadcasts.
Akin said Monday he misspoke. He apologized but said he had no plans to drop out of the Senate race.
"The good people of Missouri nominated me and I'm not a quitter. My belief is we're going to take this one forward, and by the grace of God, we're going to win this race," he told The Mike Huckabee Show, a radio program hosted by the former Arkansas governor, a favorite of religious conservatives and an Akin supporter.
American Crossroads, a pro-Republican outside funding group linked to strategist Karl Rove, said it was pulling its advertising from the Missouri race. The group said it has already spent $5.4 million in Missouri.
Mitch McConnell, the top Republican in the U.S. Senate, also said Akin should consider leaving the race.
Akin has until Tuesday evening to withdraw without a court order, or until Sept. 25 if he produces a court order to take his name off the ballot.
If he did step aside, the Missouri Republican committee would nominate a new candidate to run for the Senate. That candidate would not have to be one of his two primary opponents.
Besides distancing itself from Akin, Romney's campaign said a Romney administration would not oppose abortion in case of rape. That would be a departure from the position of his vice presidential pick, U.S. Representative Paul Ryan, who has proposed legislation that would outlaw abortion with no exception for rape.
Ryan co-sponsored a bill with Akin in the House of Representatives that would have changed the legal definition of rape to "forcible rape" to narrow access to federal funding for abortions. Critics said the measure could exempt victims of statutory rape.
McCaskill is one of the most vulnerable Senate Democrats in a state that has shifted to the right since she was elected in 2006. Recent polls had shown Akin with a 10-point lead over her.
Akin, a six-term congressman from the St. Louis suburbs, won the Republican nomination to oppose McCaskill just two weeks ago after a hard-fought three-way primary race.
(Addditional reporting by Susan Heavey and Alina Selyukh; Editing by Alistair Bell and Doina Chiacu)