BLOOMINGTON, Ind. — In many parts of the country, Republican candidates are trying to put distance between themselves and President Trump. In the Indiana Senate primary, the bruising fight is over which candidate is the more authentically Trumpian.
As the May 8 primary election approaches, the race here has taken a nasty turn, with candidates attacking one another as insufficiently aligned with the president, or way too late to Team Trump. Some Republicans worry that the tenor has the potential to bloody the winner so badly that he will be weakened in the general election contest against Senator Joe Donnelly, one of this election year’s most vulnerable Democrats.
“Of course it helps Donnelly,” said Robert T. Grand, a lawyer and powerful figure in state politics for decades. “Any division in the Republican Party helps Donnelly.”
The Indiana primary is among several, including those in West Virginia and Wisconsin, where Republicans are locked in nominating battles in states Mr. Trump won in 2016 and where the party has hoped to add to its slender two-seat majority. In Wisconsin, a Marine Corps veteran and political newcomer, Kevin Nicholson, is taking on a state senator, Leah Vukmir, for the right to challenge the incumbent senator, Tammy Baldwin. Both have deep-pocketed donors ready to bankroll an extended primary fight.
In West Virginia, a half-dozen Republicans want to challenge Senator Joe Manchin III, but three have emerged as the most formidable in a drawn-out battle, state Attorney General Patrick Morrisey, Representative Evan Jenkins and the former mining executive Don Blankenship, who went to prison for the deadly Upper Big Branch coal mining disaster in 2010 but emerged unrepentant.
Winning in all three of these states has taken on added urgency after the unanticipated retirements of Republican senators in Tennessee, Arizona and Mississippi left open seats that could suddenly be competitive.
In Indiana, Representative Todd Rokita started airing a television ad this week that labeled one of his opponents, Representative Luke Messer, a “Never Trump lobbyist” and the other, Mike Braun, a business executive, as voting for either Hillary Clinton or Barack Obama. His slogan: “Defeat the Elite.”
“It’s a legitimate three-way race,” said John Hammond, a lawyer and member of the Republican National Committee from Indiana, “and everybody will probably go right up to the line with rhetoric and negative message. It’s happening and it’s intensifying.”
He added, “All the opposition research will have been done for Joe Donnelly at that point.”
Mr. Rokita said he had no concerns that the attacks would help the incumbent Democrat. “I think this primary is very cleansing,” he said. “I want voters to know about these two guys. And I want them to know about me.”
Referring to two previous Republican presidential candidates, John R. Kasich and Mitt Romney, Mr. Rokita added: “Messer at this point is like all losing candidates, like Kasich or Romney, ‘if you beat up on me, we are all going to lose.’ Absolutely wrong. I am not waiting for Joe Donnelly to stick a knife in Luke Messer or Mike Braun in November. I am getting it all out now. Because Donnelly will stick in a knife in them.”
That kind of language has prompted concern among some of the state’s most influential Republicans.
Mr. Grand, who supports Mr. Messer, was particularly critical of Mr. Rokita trying to claim a populist mantle by deriding so-called elites. Mr. Rokita’s “elites” are something else to Mr. Grand: “People that know what’s good for the Republican Party, yes, longstanding Republicans, yes. People who know how to elect Republican candidates.”
“Or,” he asked, does Mr. Rokita “want to go back to the group that gave us Mourdock?”
That was a reference to Richard E. Mourdock, a candidate whose backing from Tea Party groups and national conservative organizations six years ago led to the defeat of a longtime incumbent Republican, Senator Richard G. Lugar, in the Indiana primary. Mr. Mourdock went on to lose to Mr. Donnelly.
Mr. Mourdock painted Mr. Lugar as out of touch with the state, and emphasized the fact that he lived in Virginia, a theme that Mr. Rokita has reprised against Mr. Messer. He has also made an issue of the fact that Mr. Messer’s wife, a lawyer, is on the payroll of an Indianapolis suburb even though she, too, lives in Virginia.
Mr. Messer, the father of two teenage daughters, said he was raised by a single parent and felt it important to be closer to his children, and said voters would understand.
A competitive primary or multicandidate field can sometimes actually reflect party strength and enthusiasm, but if the contest becomes too negative, the party can suffer.
“Where there are particularly competitive or divisive primaries, it is bad for the parties when they go to the general,” said Andrew B. Hall, a political scientist at Stanford University who has studied the subject. “Things are getting put on record that make you look weak. You alienate some of your own base. You’ve expended some of your resources.”
Mr. Donnelly has no serious opposition for the Democratic nomination, though he is already under assault from Republican-aligned groups that are spending millions of dollars to defeat him.
Each of the Republican candidates has tried to emphasize ties to Mr. Trump in a state the president won by 19 percentage points. Mr. Braun claims a Trump-like background, having built a logistics company in southern Indiana that now employs 850 people and gave him wealth that he can spend heavily on his own campaign.
He said Mr. Messer and Mr. Rokita were professional politicians, lawyers who “never practiced” but always had their eyes on the next political rung. Mr. Braun served briefly in the State Legislature.
In a candidate debate, in which Mr. Braun wore jeans and a denim shirt, he made the case harshly. In a new ad, he uses humor, carrying cardboard cutouts of the two men — dressed identically in white shirt, red tie and dark suit — and asked voters if they could tell the difference between them.
“Where is your real world experience?” Mr. Braun said in an interview. “They don’t have any.” He added: “They are creating a large avenue up the middle between two career politicians. That was a gift that kept on giving.”
Mr. Braun dismissed Mr. Rokita as a “smash mouth.”
“He’ll do and say things that might impress,” he said. “If he’s trying to act like Trump it’s kind of a poor impression.”
He also said there could be lingering damage: “When you’ve got sharp elbows, that creates a long memory for the people hit by those elbows.”
He rejected Mr. Rokita’s charge that he was a recent Republican convert, saying he had never voted for a Democrat for a federal office.
Mr. Messer, whose campaign so far has been the most measured of the three, accused Mr. Rokita of “trying to make things up.”
“It’s crazy,” Mr. Messer said. “You can’t find one interview in the entire campaign where I didn’t make the point that we need to elect President Trump. Do I agree with every single President Trump tweet? No. I’ve expressed a few times my concerns about the president. But throughout, I have supported him and voted for the president in the primary.”
All the candidates embrace some of the president’s core positions, like the need for a wall along the Mexican border, and all pledge to be a solid voice for the president’s agenda.
Mr. Rokita’s opponents say his voting record suggests otherwise: Mr. Rokita voted against the budget deal that Mr. Trump signed this year
He said he did so because the bill contained too much federal spending. But, Mr. Rokita added, because he supported Mr. Trump before his rivals and has the endorsement of people who ran the Trump campaign in the state, he can disagree with the president, something he said Mr. Messer could not do.
“Now he has to do everything he can to pander to the president and Mike Pence,” Mr. Rokita said. “Oh, the president wanted this terrible spending bill. Whereas I, in a very healthy way, can say no to things like the spending bill and still be on the side of the president.”
Even with all the friction in the primary so far, if there are safe places for the midterm elections to be a referendum on Mr. Trump, Indiana is surely among them. Republicans will pour extraordinary resources into the effort to oust Mr. Donnelly, and the president and Vice President Mike Pence, the former Indiana governor, will be able to give the senate nominee added firepower.
That gives Republicans comfort that they can endure a fractious primary. “People are very energized,” Mr. Grand said. “They are not playing into this thing that ’18 is going to be a bad year.”