Story highlights Rep. Akin is a no-show on CNN's "Piers Morgan Tonight"

The chairman of the RNC says he hopes Akin won't be at the national convention

Akin apologizes: "I never told anybody I was perfect"

Calls mount for the Republican candidate to drop out of Missouri Senate race

Republican Senate candidate Todd Akin canceled a primetime TV appearance at the last minute Monday night, shying away from the spotlight on a day he was under fire for controversial comments he made about rape.

Akin was scheduled to be on CNN's "Piers Morgan Tonight." A studio was booked and a chair was set.

But shortly before he was to appear, Akin canceled. He was editing a new ad, an activity that forced him to bow out, two people with ties to his campaign said.

"Congressman, you have an open invitation to join me in that chair whenever you feel up to it," said Morgan.

Pressure from the mainstream Republican Party mounted on the Missouri representative throughout the day 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.

McCaskill also was booked to be a guest on "Piers Morgan Tonight." She canceled earlier in the day.

Akin's remarks shifted the political focus Monday to abortion and women's rights, causing certain GOP nominee Mitt Romney's team to clarify the campaign's abortion stance.

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."

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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, Josh 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, repeatedly, 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.

"Rape is never legitimate. I used the wrong words," Akin said on Sean Hannity's syndicated radio show.

"When I was running for this race I never told anybody I was perfect. I make mistakes. But when I do make mistakes, Sean, I admit it and I tell people I'm sorry and I've done that from the bottom of my heart," he told Hannity.

Akin made it clear he would remain in the race and said he believed the people of Missouri are capable of looking beyond the mistake. "This campaign is more than just one TV interview."

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. Ryan also visited Romney headquarters in Boston.

At the White House, President Barack Obama told reporters 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.' "

Other Democrats and some Republicans piled on.

Republican National Committee Chairman Reince Priebus said he hoped Akin would not come to the national convention in Florida.

"If it was me and I had an opportunity to let someone else run to actually give ourselves a better chance of winning, I would step aside," he told CNN's Erin Burnett.

"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.

The nation's largest tea party political action committee, the Tea Party Express, similarly called on Akin to step down, describing the candidate's comments as "unfortunate and inappropriate."

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."

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."

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.

"Rape can make you pregnant. Period," Aaron Carroll, associate professor of pediatrics at the Indiana University School of Medicine and the director of the university's Center for Health Policy and Professionalism Research, wrote in an opinion piece for CNN. "If you put sperm near egg, women can get pregnant."

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."

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 raised $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."

Among Akin's constituents, reactions to his comments were mixed.

"It strikes me that this is a tempest in a teapot," said Gene Wood, who voted for Akin and plans to vote for him again.

"I think he used a word that in reflection he wouldn't use again ... But this is just a matter of semantics," he said.

Jennifer Derfeld, an independent who voted for Akin in the past but is not leaning toward him in the upcoming race, compared his comments to a slap in the face for rape victims.

"I mean either you have been raped or you have not been raped. It's not legitimate or illegitimate," she said.