JEFFERSON CITY, Mo. — Rep. Todd Akin defied the nation’s top Republicans on Tuesday and forged ahead with his besieged Senate bid, declaring that the party was overreacting to his comments that women’s bodies can prevent pregnancies in cases of “legitimate rape” and by insisting that he abandon his campaign.

Akin pledged to carry on with his quest to unseat Democrat Sen. Claire McCaskill of Missouri. But his bid faced tall obstacles: a lack of money, a lack of party support and no assurance that his apologies would be enough to heal a self-inflicted political wound.

“I misspoke one word in one sentence on one day, and all of a sudden, overnight, everybody decides, ‘Well, Akin can’t possibly win,’” he said on a national radio show hosted by former Republican presidential candidate Mike Huckabee. “Well, I don’t agree with that.”

Akin predicted that he would bounce back from the political crisis threatening his campaign, including a call from presumptive presidential nominee Mitt Romney to leave the race. The seat is pivotal to Republican hopes of regaining control of the Senate.

“I’m in this race for the long haul, and we’re going to win it,” he told radio host Dana Loesch in St. Louis.

Akin will have to rebuild without any money from the national party and with new misgivings among rank-and-file Republican voters who just two weeks ago propelled him to a comfortable victory in a hotly contested primary.

In a potential sign of his strategy, Akin appealed Tuesday to Christian evangelicals, anti-abortion activists and anti-establishment Republicans. He said he remains the best messenger to highlight respect for life and liberty that he contends are crumbling under the big-government policies of President Barack Obama.

Akin appealed to that audience directly during his interview with Huckabee, making allusions to the Sept. 11 terrorist attacks and focusing on the idea that he had misplaced a single word during a Sunday interview with St. Louis television station KTVI.

But Akin has been roundly criticized both for using the words “legitimate rape” and saying that a woman’s body has the ability to prevent conception after such an attack.

Hours earlier, Akin posted an online video in which he apologized again for his remarks. Campaign spokesman Ryan Hite said the apology was intended to cover both the reference to “legitimate rape” and Akin’s assertion that rape victims have a natural defense against pregnancy. The video will run as a 30-second ad on TV stations statewide for several days, Hite said.

Tuesday was the final day in which Akin could withdraw from the race without a court order. As the 5 p.m. deadline to withdraw neared, Republican leaders intensified their pressure on Akin to exit.

Sen. Roy Blunt issued a joint statement Tuesday with all four of Missouri’s living former Republican senators — John Ashcroft, Kit Bond, Jim Talent and John Danforth — saying “it serves the national interest” for Akin to step aside. Romney said the congressman should “accept their counsel.”

Akin provoked the political uproar when he was asked in the KTVI interview whether his general opposition to abortion extends to 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.

It’s not clear if Akin’s campaign will have the financial support to wage a prolonged advertising battle against McCaskill in the expensive St. Louis and Kansas City markets and the Republican-rich area of Southwest Missouri.

The campaign arm of the Senate Republicans has already withdrawn $5 million in advertising planned for the Missouri race. The Karl Rove-backed Crossroads organization pulled its ads, too. A fundraiser planned for next month in Washington was called off after all of the dozen GOP senators who had agreed to participate pulled out.

Crossroads President and CEO Steven Law suggested Tuesday that Akin was potentially helping Democrats retain their Senate majority by remaining in the race.

“The stakes in this election are far bigger than any one individual,” said Brian Walsh, a spokesman for the National Republican Senatorial Campaign Committee. By staying in the race, Akin “is putting at great risk many of the issues that he and others in the Republican Party are fighting for.”

Without that financial backing, Akin will need the support of social conservatives, who have formed his political base through a 12-year congressional career.

Noreen McCann, who lives in the same suburban St. Louis area as Akin, said Tuesday that his rape comment hasn’t weakened her support for him. McCann expressed frustration that Akin was being publicly flayed for his ill-chosen words while some Democrats — specifically President Bill Clinton — have survived scandals that included accusations of sexual impropriety and lies.

Akin “is a man of principle. I trust and respect his integrity and his commitment to defending American values,” said McCann, who had passed out Akin fliers on primary election day. “I think he wants to defend all innocent human life. If he misspoke, or it was in the wrong context, that is not a major problem for me.”

But other Missouri Republicans are second-guessing their support for Akin.

Steven and Carolyn Sipes, retired schoolteachers who are GOP committee members in Southwest Missouri’s Christian County, both voted for Akin in the primary. Carolyn Sipes is now doing some soul-searching prayer about whether Akin remains the best choice. Her husband believes Republicans would have a better shot of unseating McCaskill without Akin.

“If he decides to stay in, I’ll back him to the hilt,” Steven Sipes said. “I think it would be better probably if he did drop out at this point. He’s getting a lot of negative publicity.”

Akin’s campaign released an open letter Tuesday from Jack Willke, former president of the U.S. National Right to Life Committee, stating that he was “outraged at how quickly Republican leaders have deserted” Akin.

Akin “remains a strong and courageous pro-life leader — and awkward wording in one sound bite doesn’t negate that,” Willke’s statement said.