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."

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."