“This is a guy that doesn’t work the room,” said David B. Cohen, a political-science professor at the University of Akron. “It’s unclear whether he really enjoys what he does for a living right now.”
In Tuesday’s primary, Mr. Renacci faces competition for Trump voters who might again be drawn to someone who presents himself as an insurgent. His main opponent is Mike Gibbons, a wealthy investment banker who speaks admiringly of Mr. Trump’s agenda and raised money for him when he was running for president.
“I’m an outsider, and I’m blunt, and I tell the truth,” Mr. Gibbons said at a rally outside Cincinnati on Thursday, where he appeared with Senator Rand Paul, Republican of Kentucky. (“The establishment is all behind the other guy,” Mr. Paul said of Mr. Renacci, not meaning it as a compliment.)
In an interview, Mr. Gibbons said Mr. Renacci simply did not connect with people and could not beat Mr. Brown. At the rally, he was unsparing. “One of the best things I have going for me is when Jim Renacci speaks to a group, I get more votes,” he said to laughs. “I’d like to increase his speaking engagements.”
Another complication is the issue of trade.
Mr. Brown voted against the North American Free Trade Agreement as a House member and even wrote a book called “Myths of Free Trade.” When Mr. Trump imposed tariffs on imported steel and aluminum this year, Mr. Brown cheered him on.
Mr. Renacci, by contrast, has voted for trade agreements with South Korea, Colombia and Panama, and he also supported giving President Barack Obama enhanced trade-negotiating power.
“The trade issue has been difficult for Renacci because he is really your typical big-business Republican,” Professor Cohen said. “Trump’s more populist tone on issues like trade dovetails really well with Sherrod Brown’s position on trade and other populist issues that Brown has been advocating for decades.”