Three prominent conservatives backed Rep. Todd Akin's (R-Mo.) Senate bid after the deadline for him to exit the race passed on Tuesday.

Former Sen. Rick Santorum (R-Pa.) and Sen. Jim DeMint (R-S.C.), a Tea Party leader, endorsed Akin on Wednesday. Missouri Sen. Roy BluntRoy Dean BluntSenate GOP attempts to wave Trump off second Putin summit Election security bill picks up new support in Senate Overnight Defense: Fallout from tense NATO summit | Senators push to block ZTE deal in defense bill | Blackwater founder makes new pitch for mercenaries to run Afghan war MORE, who had earlier called for Akin to exit the race, issued a statement late Tuesday night supporting the lawmaker.

The endorsements come amid concerns about the GOP's chances of winning control of the Senate. Sen. Claire McCaskillClaire Conner McCaskillHistory argues for Democratic Senate gains Polling analyst: Same Dems who voted for Gorsuch will vote for Kavanaugh Pollster: Kavanaugh will get Dem votes MORE (D-Mo.) was considered one of the most vulnerable senators running for reelection until Akin made his controversial comment about "legitimate rape." Polls have shown her leading in the race since then.

Several prominent members of the GOP, including presidential nominee Mitt Romney, called for Akin to step down, but the lawmaker refused.

He's collected a small trickle of conservative supporters since then, including Newt Gingrich, who appeared with Akin at a fundraiser on Monday, and Mike Huckabee.

But the new set of endorsements, and their fundraising machines, could be a big boon to his bid. In particular, DeMint's PAC, the Senate Conservatives Fund, aided several senators in 2010.

"If Republicans are to win back the Senate and stop President Obama's liberal agenda, we must defeat Sen. Claire McCaskill in Missouri. Her support of President Obama's job-killing, big-spending policies are sending our country into an economic abyss," Santorum and DeMint said in a joint statement announcing their support for Akin.

"Todd Akin is a principled conservative who is committed to winning and fighting for freedom in the U.S. Senate," the statement continues. "Todd will work to stop reckless spending, stop the out-of-control debt, repeal the government takeover of healthcare, support our military and defend life at every stage."

Akin, in a statement, thanked Santorum and DeMint for their support.

"I am proud to have two of our country's leading conservatives endorse me today," he said. "Rick Santorum and Jim DeMint know that Claire McCaskill has voted with President Obama 98% of the time, she was the deciding vote for Obamacare and has voted to increase our national debt by $6.9 trillion. Our country can't afford another six years of the liberal agenda of Claire McCaskill."

Blunt, in his endorsement, also emphasized the importance of winning the upper chamber.

"Congressman Akin and I don’t agree on everything, but he and I agree the Senate majority must change. From Gov. Romney to the county courthouse, I'll be working for the Republican ticket in Missouri, and that includes Todd Akin," he said in a statement.

Republicans need a net gain of four seats, if Obama wins reelection, to take control of the Senate next year. The National Republican Senatorial Committee vowed not to spend in Missouri after Akin refused to leave the race.

The NRSC did not rule out spending in the race in the future.

“There is no question that for Missourians who believe we need to stop the reckless Washington spending, rein-in the role of government in people’s lives, and finally focus on growing jobs in this country that Todd Akin is a far more preferable candidate than liberal Senator Claire McCaskill.  As with every Republican Senate candidate, we hope Todd Akin wins in November and we will continue to monitor this race closely in the days ahead," said NRSC executive director Rob Jesmer in a statement.

Democratic Senatorial Campaign Committee spokesman Shripal Shah charged the GOP with playing politics.

"No one should’ve been fooled by the party’s faux outrage and their ensuing change of course because as the Republican establishment is making clear today, the Akin backlash was never about principle, it was purely about politics," he said in a statement.

“The fact is that in today’s GOP, Todd Akin actually represents the party’s mainstream.  Scott Brown, Dean HellerDean Arthur HellerHistory argues for Democratic Senate gains Senate Dems build huge cash edge in battlegrounds Jacky Rosen hits Dean Heller over health care in first negative ad MORE, Linda McMahon and Tommy Thompson all support a Republican agenda that would inflict Todd Akin’s views on the nation. All Republican candidates across the country are going to have to answer for Todd Akin’s extremism on election day," he said.

And McCaskill indicated during an appearance on MSNBC's "The Last Word" that she doesn't believe the race is won yet, despite Akin's decision to stay in.

And she framed the race as a choice between her own moderate record and Akin's more extreme past, an argument she's made previously in ads and on the stump. During the show she highlighted a number of what she portrayed as his extreme stances, including his position against hate-crime legislation and a registry for sex offenders.

But the Senate race in Missouri goes further than just policy positions, she said.

"I don't think the problem is what Todd said. The problem is what Todd believes. That is really the essence of this race. What are his beliefs? And his beliefs, I believe, are such that Missourians — honestly ... his beliefs would be painful for Missouri families," she said.

— This story was last updated at 2:51 p.m.