Rep. Todd Akin vowed to fight on in his embattled Senate campaign, but a significant deadline loomed Tuesday that was bound to intensify pressure on the Missouri congressman to abandon the race.

Aiken came under fire for his comments that women's bodies can prevent pregnancies in cases of "legitimate rape." He spent Monday trying to salvage his once-promising challenge of incumbent Democrat Claire McCaskill.

But ominous signs were mounting against the six-term legislator from suburban St. Louis, mostly notably the apparent loss of millions of dollars in party advertising money and waning political support among fellow Republicans.

The decision has some urgency. Missouri election law allows candidates to withdraw 11 weeks before Election Day. That means the deadline to exit the Nov. 6 election is 5 p.m. Tuesday. Otherwise, a court order would be needed to remove a name from the ballot.

"I was told the decision has to be made by 5 tomorrow, but I was calling you and letting you know that I'm announcing today that we're in," Akin told radio host Sean Hannity.

In a radio interview with former Republican presidential candidate Mike Huckabee, Akin repeatedly apologized for the remarks but also vowed to stay in the race.

"The good people of Missouri nominated me, and I'm not a quitter," Akin said.

Akin cancelled a scheduled appearance with Piers Morgan on CNN, prompting the host to show an empty chair.

"Congressman," the CNN host addressed Rep. Todd Akin, a Missouri Republican, "you have an open invitation to join me in that chair whenever you feel up to it.

"If you don't keep your promise to appear on the show, then you are what we would call in Britain a gutless little twerp."

Within minutes, the phrase "gutless little twerp" was streaking around the Internet, and the Morgan stunt garnered Twitter's ultimate accolade -- a parody account, @AkinEmptyChair

The uproar began Sunday, when St. Louis television station KTVI aired an interview in which Akin was asked if he would support abortions for women who have been raped.

"It seems to me, first of all, from what I understand from doctors, that's really rare. If it's a legitimate rape, the female body has ways to try to shut that whole thing down," Akin said.

Later Sunday, Akin released a statement saying that he "misspoke" during the interview.

In the interviews with Huckabee and Hannity, he apologized repeatedly, acknowledging that rape can lead to conception.

"Rape is never legitimate. It's an evil act. It's committed by violent predators," Akin said. "I used the wrong words the wrong way."

New Jersey Governor Chris Christie called the comments "assinine"

The Associated Press contributed to this report