DES MOINES, Iowa — As a medical doctor, Kentucky Sen. Rand Paul has a rare set of credentials at the intersection of science and politics. But the glare of the 2016 presidential race is searing, and under it, Paul had a rough week.

On Friday night in Iowa, Paul faced likely voters in the state’s leadoff nominating caucuses for the first time since answering questions about a measles outbreak centered in California. Paul said Monday that he had heard about “many tragic cases” of children who got vaccines and ended up with “profound mental disorders.”

That assertion has no basis in medical research, and Paul clearly was still upset on Friday about how his comments had been received.

“It may be a little because I’m a doctor, but really I think it’s inaccuracies” fueled by reporters, he told The Associated Press. “From my point of view, that’s frustrating.”

Paul’s supporters in Iowa rallied around him, bestowing on him “more credibility than other would-be presidential candidates on the issue,” said former Iowa Republican Party co-chairman David Fischer, a Paul supporter.

But the episode probably took a toll on Paul, a libertarian who intends to try to highlight his background as a physician as an advantage if a possible White House campaign.

Republicans in Washington distanced themselves from Paul this past week, and none went out of his way to defend him.

“As a doctor, I believe all children should be vaccinated,” said Sen. John Barrasso, R-Wyo., an orthopedic surgeon. It was a line he repeated several times when asked about the uproar.

Senate Majority Leader Mitch McConnell, who has said he would support a run by Paul, made no secret of his disagreement with Paul about the value of childhood vaccinations.

“As a victim of polio myself, I’m a big fan of vaccinations,” McConnell, R-Ky., told reporters.

Paul’s immunization comments were the latest, and most inflammatory, example of the challenge he faces as the one of two doctors – along with Ben Carson, a retired neurosurgeon – among the more than dozen GOP contenders.

Paul is viewed as an expert on science in an age where anyone with Internet access can check his statements. He also is a politician and a congressman’s son whose platform revolves around a distrust of government shared by some in both parties.

“Physicians look at things differently,” Paul told the AP. “We don’t think of things so much in partisan terms. We think of them as problems. And the problem has to be fixed.”

When it comes to vaccinations, he said, “the science doesn’t show a relation” between them and mental disorders.

Carson, who has generated a following in Iowa and nationally among conservatives, said this past week that he has heard stories of brain damage resulting from vaccinations. But he was quick to add that in his career as a pediatric surgeon, he had never been presented with such a case.

“There have been many stories like that, that have circulated,” Carson said. “Have I ever encountered one? No.”

Paul’s words about a medical issue have raised eyebrows before.

Last fall, when the Ebola virus reached the United States in a few isolated cases, Paul told a group of college students that the disease can spread from an infected person to someone standing 3 feet away. He called Ebola “incredibly contagious” and suggested it could spread at a cocktail party attended by someone who is symptomatic.

Paul also suggested that the Centers for Disease Control and Prevention made the transmission of Ebola sound similar to that of AIDS. Ebola, he said, is easier to contract.

“You’re not going to get AIDS at a cocktail party. No one’s going to cough on you and you’re going to get AIDS. Everybody knows that. That’s what they make it sound exactly like,” Paul said. “But then you listen to them closely, they say you have to have direct contact. But you know how they define direct contact? Being within 3 feet of someone.”

Health authorities worldwide have said that Ebola is only transmitted through direct contact with bodily fluids – and that blood, vomit and feces carry the most virus.

Such political missteps are noticed by those paying early attention to the presidential race.

Gwen Ecklund, the Republican Party chairwoman in Iowa’s GOP-heavy Crawford County is not yet aligned with any candidate. She said Paul’s medical credentials add weight to his words.

“I think people pay more attention when Sen. Paul is saying it, more than when others do,” she said.