The special election race for the open House seat in Ohio’s 12th Congressional District is making for strange bedfellows, with President Trump and Gov. John Kasich pushing to help Republican Troy Balderson beat Democrat Danny O’Connor in a tight race.
The stormy Trump-Kasich relationship dates to a series of testy exchanges in the 2016 presidential race and could reach a boiling point in 2020 if Mr. Kasich starts a primary bid against Mr. Trump, which he says he is considering.
For now, though, the two are working toward the shared goal of making sure Mr. Balderson, a state senator, wins Tuesday’s special election and gives the GOP a jolt of confidence heading into the midterm elections that are historically bad for the sitting president’s party.
“I think it is one of these things where the common enemy in the Democrats are going to bring people together who ordinarily don’t agree on much of anything, and Kasich I think has probably been the most outspoken Trump opponent in the Republican Party,” said Paul A. Beck, professor emeritus of political science at Ohio State University.
“I think they are both focused on a contest that could go either way,” Mr. Beck said. “It is very clear to me that just looking at the flow of money that Republicans think they can lose this contest.”
Mr. O’Connor’s campaign has outspent Mr. Balderson by $260,000, but outside groups have more than made up the difference, investing about $5 million more than their Democratic counterparts, according to data from the Center for Responsive Politics.
The Congressional Leadership Fund, a super PAC aligned with House Speaker Paul D. Ryan, has poured $2.6 million into television ads tearing down Mr. O’Connor and building up Mr. Balderson, including a spot that started running this week featuring Mr. Kasich.
“Troy Balderson was a partner of mine as a member of the Ohio legislature and he helped in cutting taxes and turning Ohio around,” Mr. Kasich says in the ad. “Troy shares our common-sense values on important issues that face us today.”
The ad is slated to run through election day and will be on air when Mr. Trump visits Delaware, Ohio, on Saturday to hold a rally for Mr. Balderson.
“Troy is strong on crime and Borders, loves our Military, our Vets and our Second Amendment,” Mr. Trump tweeted this week. “Troy will strongly protect your Social Security and Medicare!”
Former Vice President Mike Pence campaigned with Mr. Balderson this week in Ohio.
Mr. Balderson needs all the help he can get, according to a Monmouth University Poll released Wednesday that showed the race, which he led by 10 points last month, is now a dead heat.
“This is still a Republican-leaning district with many metrics that continue to favor Balderson, but growing Democratic enthusiasm has made this race surprisingly competitive,” said Patrick Murray, director of the Monmouth University Polling Institute. “O’Connor’s chances hinge on generating a larger-than-usual share of the vote from the suburbs north of Columbus.”
Mr. Balderson said he always expected the race will be close and said he is confident that his resume and the support he is receiving from Mr. Trump, Mr. Kasich and former Rep. Pat Tiberi, whose seat is being contested, will put him over the top.
“Troy has a proven record of cutting taxes, balancing budgets, and fighting for the middle class, and he will work with the president to make the middle-class tax cuts permanent, something Dishonest Danny O’Connor refuses to do,” said Jenna Knepper, a campaign spokeswoman.