The storm of controversy surrounding Rep. Todd Akin’s (R-Mo.) “legitimate rape” comment could cost him more than 5 percentage points if he remains in the hotly contested Missouri Senate race, according to campaign experts who have studied the historical impact of scandal on candidates.

Chad Long, a St. Edward’s University political scientist who has examined how political controversy has affected incumbent senators, said these types of verbal miscues usually result in a 5-point dip in November.

But Akin could take a bigger hit because he is a challenger, Long said in an interview.

“I would expect it actually, maybe, hurts challengers more. As an incumbent, you built up this level of good will among your constituents. You have done a lot of good things for the state, and so if you make a misstep like this, it is going to be weighed against the … years of service you put in,” Long said.

Akin set off a firestorm Sunday when, while explaining his opposition to abortion, he told a local TV station that it is rare for women to become pregnant in cases of “legitimate rape."

“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.

Akin has apologized for his remarks and in a new campaign ad asks Missouri voters to forgive him for his mistake.

On Tuesday, he told conservative talk radio host Mike Huckabee “we are going to continue with this race for the U.S. Senate.”

But the pressure on him to withdraw from the election reached a fever pitch when Republican presidential candidate Mitt Romney joined several GOP senators — including Missouri’s Roy BluntRoy Dean BluntRussian assault on 'American idea' enables Trump to take tough action Eleven lawmakers have used campaign funds to pay NRA dues: report Kimmel writer tweets amount NRA has given lawmakers in response to shooting prayers MORE — in calling for Akin to abandon his campaign.

Long analyzed political scandals from 1974 to 2008 in incumbent senatorial elections, counting 91 instances.

They were broken down by category such as crime, abuse of office, financial, moral, statements and other. Long counted 21 cases of scandals related to statements made by candidates.

He found a 5.33 percentage-point disadvantage for incumbents involved in a scandal about comments made.

Long found that scandals of a “moral” nature were the most damaging, resulting in a 6.51-point drop.

Akin is following a trend set by past candidates who refused to drop out of a race following serious blunders, often leading to disastrous results.

One of the closest parallels comes from the 1990 Texas gubernatorial race, which pitted Republican businessman Clayton Williams against Ann Richards, the Democratic state treasurer.

While preparing for a cattle roundup on his ranch that March, Williams remarked to a group of campaign workers and reporters that the weather, which was foggy and cold, was like rape.

“If it's inevitable,” Williams said, “just relax and enjoy it.”

Williams apologized a few days later. But it was just the first in a series of gaffes — including refusing to shake Richards’s hand after a debate that October — that sank his campaign. Despite leading early in the polls by a large margin, Williams narrowly lost, 49 percent to 47.

More recently, former Virginia Sen. George Allen (R) lost his reelection bid against Jim Webb (D-Va.) in 2006 after he was caught on video calling a Webb-campaign cameraman, who was of Indian descent, “macaca,” a word many interpreted to be a racial slur.

Allen, who is running again this year against former Gov. Tim KaineTimothy (Tim) Michael KaineSave lives, restore congressional respect by strengthening opioids’ seizure Overnight Finance: Lawmakers, Treasury look to close tax law loopholes | Trump says he backs gas tax hike | Markets rise despite higher inflation | Fannie Mae asks for .7B Bipartisan Senate group says they have immigration deal MORE, lost that election by 0.4 percentage points.

A poll by the Democratic-leaning firm Public Policy Polling, conducted after Akin’s remark, showed him continuing to lead Sen. Claire McCaskillClaire Conner McCaskillMcCaskill welcomes ninth grandson in a row Dem group launches M ad buy to boost vulnerable senators Senate Dems block crackdown on sanctuary cities MORE (D-Mo.) 44 percent to 43.

The National Republican Senatorial Committee has said it would not invest a planned $5 million in the Missouri Senate race if Akin persists with his campaign. The outside group Crossroads GPS announced Monday it was pulling its ads out of Missouri.

The loss of funding from fellow Republicans and conservative allies might have the largest impact on Akin’s chances if he stays on the ballot, said Adams State College political science Professor Stephen Roberds, who has also studied the impact of congressional scandals.

“Akin's most serious problem is that the GOP Senate election committee, Karl Rove's group and others are pulling back ads and money,” Roberds said in an email to The Hill. “If he has limited campaign funds and is seriously outspent by McCaskill, his chances go down. So the scandal may have an indirect effect through the loss of money.”

Long said it is rare for a candidate to drop out of a race after a verbal gaffe. Instead, the personality that attracts Senate candidates also ensures they rarely quit.

“The power and prestige that accompanies a seat in the United States Senate clearly makes one loath to give it up,” Long concluded in his study. “This willingness to stand and fight — even in a weakened state — is a trait that helped them to get elected in the first place.”

Prior to his Senate bid, Akin was elected six times as the congressman for Missouri’s 2nd district.

Roberds said criminal charges are usually needed to spur a candidate to step aside. An example is the money-laundering charges that brought down former House Majority Leader Tom DeLay (R-Texas) in 2005.

“Criminal allegations, indictments, convictions are the most serious impediments to candidates with scandals,” Roberds said. “Punishments by the congressional ethics committees are also important.”

Voters tend to find sexual scandals most objectionable, according to Long’s study.

Former Rep. Anthony Weiner (D-N.Y.) resigned last year after it came to light that he had been sending inappropriate pictures of himself to women through Twitter.

Illinois Republican Jack Ryan withdrew from the 2004 race for the state’s open U.S. Senate seat after records from his custody battle with his ex-wife were unsealed, revealing lurid accusations from Ryan’s former spouse and paving the way for Barack ObamaBarack Hussein ObamaOvernight Energy: Dems ask Pruitt to justify first-class travel | Obama EPA chief says reg rollback won't stand | Ex-adviser expects Trump to eventually rejoin Paris accord Overnight Regulation: Trump to take steps to ban bump stocks | Trump eases rules on insurance sold outside of ObamaCare | FCC to officially rescind net neutrality Thursday | Obama EPA chief: Reg rollback won't stand Ex-US ambassador: Mueller is the one who is tough on Russia MORE to win his first national office.