The first surveys to be released after the debate on Tuesday show the Trump-endorsed Republican nominee has increased his chances of winning by as much as three percentage points.

Polls conducted by co/efficient and Insider Advantage, carried out between October 26 and 28, show Oz could be opening up a lead over his Democrat rival with the celebrity doctor gathering an estimated 48 percent of the vote against Fetterman’s 45 percent. A poll by Wick dated between October 26 and 27 gives Oz three additional percentage points, estimating he is now backed by 48 percent of voters compared to Fetterman’s 46 percent.

However, the Insider Advantage poll drew some criticism online, with an expert saying the sample lacked a sufficient amount of voters under 40, a key base for Fetterman.

“This is the first poll of the cycle that actually made me laugh out loud,” Tom Bonier, CEO of the political consulting firm TargetSmart, tweeted in response. “The likely voter sample has voters under the age of 40 at 14%. They were 25% of the electorate in ‘18 and 28% in ‘20. This poll should be entirely ignored.”

Despite the apparent poll swing, voters’ overall opinion of Oz remains significantly less positive than Fetterman’s.

According to the co/efficient poll, 42.9 percent of respondents have a favorable view of Fetterman now, against 49.5 percent who have an unfavorable view. On the other hand, only 37 percent of respondents have a favorable view of Oz, and 46 percent have an unfavorable opinion.

Despite Fetterman now trailing in some polls, polling website FiveThirtyEight still has the Democrat as “slightly favored” to win the state’s Senate race, with a 58 in 100 chance of victory.

Concerns and doubts raised by the Oz campaign around Fetterman’s health and fitness to serve in the aftermath of a stroke may have played a role in eroding Fetterman’s lead in the Senate race, as could the debate on Tuesday.

The debate, which revealed Fetterman’s ongoing struggles with the impact of a health scare that could have taken him out of the race completely, was the climax of a campaign that has been particularly ill-tempered on both sides.

The two candidates have been exchanging mockery and accusations for months, with Fetterman portraying Oz to Pennsylvania voters as an outsider who was distant from their problems and interests, and Oz presenting Fetterman as a candidate who would be soft on crime and drugs.

Oz’s rhetoric has escalated since Fetterman’s return to the campaign trail after suffering a stroke in May. The celebrity doctor has repeatedly cast doubt over whether the Lieutenant Governor is fit to serve as Pennsylvania’s senator, and still asks that Fetterman release his full medical records.

Fetterman has already shared a letter from his doctor which said he had “no work restrictions and can work full duty in public office.”

Speaking to Newsweek recently Thomas Gift, founding director of University College London’s Centre on U.S. Politics, said: “You’d be hard pressed to find any midterm race in the country that’s more juvenile than Pennsylvania’s contest between John Fetterman and Dr. Oz—and that’s saying something.”