Rep. Todd Akin (R-Mo.) trails Sen. Claire McCaskillClaire Conner McCaskillSenate moderates hunt for compromise on family separation bill Election Countdown: Family separation policy may haunt GOP in November | Why Republican candidates are bracing for surprises | House Dems rake in record May haul | 'Dumpster fire' ad goes viral Hillicon Valley: Verizon, AT&T call off data partnerships after pressure | Tech speaks out against Trump family separation policy | T-Mobile, Sprint make case for B merger MORE (D-Mo.) by double digits in their Missouri Senate race, according to a survey released Thursday from conservative polling outlet Rasmussen.

McCaskill leads with 48 percent support, while Akin has 38 percent.

A previous survey from liberal-leaning Public Policy Polling, conducted and released only one day after Akin’s controversial “legitimate rape” remark, showed the Missouri congressman with a 44 to 43 percent lead.

The Rasmussen result marks an astonishing drop for Akin and indicates Republicans' worst fears could come true — that Akin's candidacy will cost them a Senate seat. Previous polls showed McCaskill was vulnerable and Akin was leading her.

Republicans only need a net gain of four seats — if President Obama wins reelection — to take control of the Senate. McCaskill was one of their top targets. But the National Republican Senatorial Committee told Akin if he remains in the race, they will pull their funds.

The GOP has put intense pressure on Akin to withdraw. GOP standard-bearer Mitt Romney on Tuesday personally called on Akin to stand down, and several Republicans senators have echoed that sentiment, as have prominent conservative bloggers.

McCaskill, meanwhile, has said it's not her place to say what Akin should do.

And Democrats were quick to push back against the poll, saying Rasmussen has a conservative bias and is in cahoots with GOP party leadership in trying to pressure Akin out of the race.

“Everyone knows that Rasmussen is a tool of the Republican establishment in Washington,” Democratic Senatorial Campaign Committee press secretary Shripal Shah told The Hill.

A McCaskill campaign aide added that “it’s just not inline with what we’re seeing in our internal polling.”

“There’s a concerted [GOP] effort to get Todd Akin to bow out,” he said. “So it’s quite a coincidence that this poll came out right after someone in his campaign said he would reevaluate if he was down by 7 to 9 percent…we were just out [polling] in the field yesterday and it showed we’re in a dead heat.”

The Republican message heading into the Republican National Convention next week has been upended by Akin’s remark that pregnancies from rape are “really rare” and that in a “legitimate rape, the female body has ways to try to shut that whole thing down.” Democrats have used the comment as part of their longtime contention that GOP is waging a war on women.

Vice presidential candidate Rep. Paul RyanPaul Davis RyanTrump backs down in rare reversal Trump, GOP launch full-court press on compromise immigration measure Meadows gets heated with Ryan on House floor MORE (R-Wis.) denounced Akin’s comments as “outrageous” and “over the pale.”

The Daily reported on Wednesday that an aide close to Akin said if he remains within 5 percentage points of McCaskill he was committed to staying in, but if he falls behind by 7 or more, “that gets difficult.”

Akin did not withdraw by a Tuesday deadline that would have marked the easiest way to resign as the GOP nominee. He can still step down but the process gets more complicated and the election gets closer.

A call to the Akin campaign has not been returned.

— This story was updated at 12:57 p.m.