CNN — Incendiary remarks by a Republican Senate candidate shifted the political focus on Monday to abortion and women's rights, causing certain GOP nominee Mitt Romney's team to clarify the campaign's abortion stance.

Pressure from the mainstream Republican Party mounted on Rep. Todd Akin of Missouri to drop his bid to unseat Democratic Sen. Claire McCaskill in November because of his comments about "legitimate rape" and opposing abortion in rape cases.

Top congressional Republicans, including House Speaker John Boehner, Senate GOP leader Mitch McConnell and Sen. John Cornyn of Texas advised Akin to spend time considering what is best for his family, party and country -- political code for urging him to withdraw.

"What he said is just flat wrong in addition to being wildly offensive to any victim of sexual abuse," McConnell said in a statement. "Although Representative Akin has apologized, I believe he should take time with his family to consider whether this statement will prevent him from effectively representing our party in this critical election."

The National Republican Senatorial Committee headed by Cornyn has advised Akin that it will not support his campaign if he stays in the race, a source from the group told CNN.

In an interview on Monday with WMUR television in Manchester, New Hampshire, Romney echoed the sentiment of other GOP leaders, according to a tweet from the station's political director, Kevin McElveen:

"@MittRomney on if Akin should end senate bid- 'he should spend 24 hours considering what will best help the country at this critical time."

Missouri election rules allow a candidate to withdraw with little difficulty through Tuesday, which is 11 weeks prior to the Nov. 6 election.

After Tuesday, the candidate must get a court order and pay for any necessary reprinting of ballots. The state Republican Party would choose another candidate to run against McCaskill, considered one of the most vulnerable senators in the country.

Akin apologized Monday for what he called a serious error in using the wrong words when he stated in an earlier interview that "legitimate rape" rarely resulted in pregnancy.

"I was talking about forcible rape," Akin said on former Arkansas Gov. Mike Huckabee's radio show. "It was absolutely the wrong word."

Akin made it clear that he would remain in the race. "The good people of Missouri nominated me, and I'm not a quitter," he told Huckabee.

Romney's camp distanced itself from the Missouri Republican, who is in a race viewed as crucial for determining which party will control the Senate next January.

In addition, the controversy drew attention away from the economic themes of Romney's campaign in the run-up to the Republican National Convention next week in Tampa, Florida. Romney and his running mate, Rep. Paul Ryan of Wisconsin, held a joint town hall-style campaign event Monday in New Hampshire.

At the White House, President Barack Obama told reporters at an unscheduled news conference that Akin's remarks were "offensive" and didn't make sense. Asked if Akin should withdraw, Obama said that was up to Missouri Republicans.

Earlier, Romney told National Review Online the comments by Akin were "insulting, inexcusable, and, frankly, wrong."

"What he said is entirely without merit and he should correct it," Romney said, according to the website.

When news of Akin's comments broke Sunday, the Romney campaign responded by declaring a definitive stance on one of the most volatile political issues in the country.

A campaign statement on Sunday night said the former Massachusetts governor and Ryan differed with Akin on the matter and that "a Romney-Ryan administration would not oppose abortion in instances of rape."

The issue is particularly sensitive for Ryan, a devout Catholic and staunch anti-abortion politician who has previously expressed opposition to abortion in all cases except when the life of the mother is endangered.

A Romney-Ryan campaign official, speaking on condition of not being identified, confirmed to CNN that Ryan's personal view opposes abortion in the case of rape. The campaign official said Ryan's stance differed with Romney's view, which was described in the statement on Sunday and is the formal position of the GOP presidential ticket.

Democrats challenged the Romney-Ryan team on the issue.

"While Mitt Romney and Paul Ryan are working overtime to distance themselves from Rep. Todd Akin's comments on rape, they are contradicting their own records," said an Obama campaign statement Monday. "Mr. Romney supports the Human Life Amendment, which would ban abortion in all instances, even in the case of rape and incest. In fact, that amendment is a central part of the Republican Party's platform."

It also said that Ryan worked with Akin "to try to pass laws that would ban abortion in all cases, and even narrow the definition of 'rape.' "

At his news conference, Obama responded to the first question he received -- about the Akin comments -- by tying them to policies of Romney and Ryan.

"What these comments do underscore is why we shouldn't have a bunch of politicians, a majority of whom are men, making health care decision on behalf of women," Obama said.

Other Democrats and some Republicans piled on.

"Congressman Akin's statement is another manifestation of the total disregard and disrespect of women by Republican leaders," House Democratic leader Nancy Pelosi said in a statement, adding that it was "almost impossible to believe that any political leader would suggest that any case of rape is 'legitimate.' "

In Massachusetts, Republican Sen. Scott Brown called on Akin to drop out of the race because of the "outrageous, inappropriate and wrong" comments.

"There is no place in our public discourse for this type of offensive thinking," said Brown, a moderate in a tough re-election battle against Democrat Elizabeth Warren. "Not only should he apologize, but I believe Rep. Akin's statement was so far out of bounds that he should resign the nomination for U.S. Senate in Missouri."

However, one of the nation's most prominent conservative organizations rallied to Akin's defense. Top officials from the Family Research Council said Akin is the target of a Democratic smear campaign, and they also chided Republicans calling for him to step down.

Connie Mackey, who heads the group's political action committee, said the organization "strongly supports" Akin.

"Todd Akin is getting a really bad break here," Mackey told reporters. "I don't know anything about the science or the legal implications of his statement. I do know politics, and I know 'gotcha' politics when I see it."

Mackey also said that Republicans calling on Akin to apologize or drop out should get "backbone." At the same time, Mackey and the group's president, Tony Perkins, were less critical of Romney's condemnation of Akin.

"The Romney campaign as well as now Paul Ryan have made very clear where they stand in the issue of life," Perkins said. "We are not going to allow people to divide conservative voters in this process. We are going to keep our eye on the big picture."

Akin's controversial comments give Obama and Democrats an opportunity to further strengthen their advantage with women voters -- a demographic that already favors them, according to the polls.

The controversial remarks about whether abortion should be legal in the case of rape were made in an interivew with Missouri television station KTVI. A clip of the interview was posted online by the liberal super PAC American Bridge. In it, Akin explained his opposition by citing unnamed bodily responses that he said prevented pregnancy.

"First of all, from what I understand from doctors, that's really rare," Akin said of rape-induced pregnancy.

"If it's a legitimate rape, the female body has ways to try to shut that whole thing down," Akin continued. He did not provide an explanation for what constituted "legitimate rape."

He added: "But let's assume that maybe that didn't work or something. You know I think there should be some punishment, but the punishment ought to be on the rapist and not attacking the child."

In a statement on Sunday, Akin wrote that he misspoke in the interview and he maintained his opposition to abortion for victims of rape. His radio interview on Monday offered a stronger apology.

Statistics on pregnancies that result from rape are difficult to produce, since rape is a crime that often goes unreported.

The Rape, Abuse & Incest National Network, along with Planned Parenthood, each estimate that 5% of rapes lead to pregnancy. A 1996 study from the Medical University of South Carolina found the same percentage, adding that 32,101 pregnancies occurred annually from rape.

Akin, a six-term U.S. congressman, touted his socially conservative values on the primary campaign trail.

He opposes abortion in all circumstances and has said he also opposes the morning after pill, which he equates to abortion.

McCaskill responded almost immediately to her opponent's comments, writing Sunday on Twitter: "As a woman & former prosecutor who handled 100s of rape cases, I'm stunned by Rep Akin's comments about victims this AM."

She later released a statement condemning her rival as "ignorant about the emotional and physical trauma brought on by rape."

"The ideas that Todd Akin has expressed about the serious crime of rape and the impact on its victims are offensive," she continued. McCaskill's website also splashed Akin's comments across the homepage, and included a link where supporters could donate money to McCaskill's campaign.

Republicans consider McCaskill, first elected in 2006, highly vulnerable in her bid for a second term. Ahead of the GOP primary, a Mason-Dixon poll showed the senator falling behind Akin and the two other main GOP primary competitors in hypothetical match ups among registered Missouri voters.

Akin was one of the first members of Congress to join the Tea Party Caucus in 2010 and has easily won reelection in recent years. The lawmaker has raised a notable $2.2 million this cycle, as of July 18.

Before the new controversy, the top nonpartisan political handicappers had rated the Missouri race a "toss-up."

On Monday, Tea Party Nation founder Judson Phillips called for Akin to drop out of the race, writing: "Control of the Senate could come down to this race and Todd Akin, whose ego is much bigger than his brain, may cost the Republican's control of the Senate."

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CNN's Peter Hamby, Paul Steinhauser, Kevin Liptak, Dana Bash and Ashley Killough contributed to this report.

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