**Watch the full debate with Ohio GOP Senate candidates held at Fox 8 News in the video above.

(THE HILL) — Ohio GOP Senate candidate J.D. Vance leads the Republican primary field in a new Fox News poll released Tuesday, an indication that he’s enjoying a boost from a late endorsement from former President Trump.

Vance, the author of “Hillbilly Elegy,” led the pack with 23 percent support primary voters, more than doubling the 11 percent support he got in the same poll in March. Former state Treasurer Josh Mandel, Vance’s main primary rival, came in second with 18 percent, a drop from 20 percent in March.

Investment banker Mike Gibbons, Ohio state Sen. Matt Dolan (R) and former Ohio Republican Party Chairwoman Jane Timken rounded out the top five, with 13 percent support, 11 percent and 6 percent, respectively. Gibbons’s support nosedived from 22 percent in March, while Dolan’s rose from 7 percent and Timken’s dropped from 9 percent.ADVERTISING

Those numbers indicated that Vance’s improvement likely came mostly from voters who previously backed Gibbons.

In a sign the race remains in flux, 25 percent of voters — a plurality in the poll — said they remain undecided. Fifty-one percent of respondents who said they back a candidate also said they could change their minds.

But still, the poll marks a significant improvement for Vance, who is waging a full-court press to inundate voters with news of Trump’s endorsement, which came on April 15, shortly before the May 3 primary.

Trump won Ohio twice by about 8 points and remains overwhelmingly popular with Republicans. Forty-two percent of primary voters said his imprimatur makes them more supportive of Vance, while just 23 percent said it made them less supportive. Another 27 percent said the endorsement had no effect.

Vance has looked to saturate voters’ minds with news of the endorsement by appearing ata rally last weekend with Trump and also holding several events with Donald Trump Jr., the former president’s eldest son.

Vance had previously been polling in the middle of the field, but a survey from a supportive super PAC released last week also showed him jumping into the lead after winning Trump’s backing. Observers questioned whether Trump’s backers would be cool to Vance over critical comments he made in 2016 about the real estate mogul’s White House bid, but Trump sought to tamp down any lingering disgruntlement in his endorsement.

“Like some others, J.D. Vance may have said some not so great things about me in the past, but he gets it now, and I have seen that in spades. He is our best chance for victory in what could be a very tough race,” Trump said.

The winner of the GOP primary is expected to take on Rep. Tim Ryan (Ohio), the prohibitive favorite in the Democratic primary, in the general election later this year.

The poll, which was conducted April 20 to April 24, included 906 randomly selected Ohio Republican primary voters. It has a margin of sampling error of 3 percentage points.