GNAW BONE, Ind. — Drunken driving, self-dealing and false advertising.

Those are just some of the charges voters here are sifting through in a brutal three-way Republican primary that will determine who gets to take on Sen. Joe Donnelly, D-Ind., in November. That contest on May 8 is one of a handful across the country that will determine which party controls the Senate next year, and Republicans believe they have a good shot at winning the seat.

The primary in Vice President Mike Pence's home state has turned personal largely because there's hardly a whit of policy difference among the three GOP candidates — Reps. Todd Rokita and Luke Messer, and former state Rep. Mike Braun. They're all against abortion, taxes and the growth of entitlement spending, and they're all doing their best to portray themselves as the second coming of President Donald Trump.

If it comes down to who is the most Trump-like, Braun should have the edge.

He took the political establishment here by surprise, dumping millions of dollars of his own money into ads that introduced him to voters and framed his opponents as twin denizens of the Washington "swamp" that the president often rails against.

In one ad, Braun, 64, dressed in his trademark blue shirt with sleeves rolled, walks around with cardboard cutouts of Rokita and Messer, both in suits and matching red ties, and asks voters if they can tell his rivals apart. Spoiler alert: They can't.

Like Trump, Braun has focused on his business acumen — in his case an auto-parts distributorship. And while critics note that he voted in Democratic primaries for many years and worked legislative levers in the Statehouse to try to win tax breaks for the timber industry, in which he has a personal stake, neither argument make him seem less like the president.

Trump won Indiana with 56 percent of the vote in 2016.

Candidates Mike Braun, left, Luke Messer and Todd Rokita give opening statements from the Indiana Republican Senate Primary Debate at Emmis Communications in Indianapolis on Feb. 20, 2018. Michelle Pemberton / The Indianapolis Star via AP file

Braun lumps his primary opponents together with Donnelly, saying that the incumbent, Messer and Rokita have failed to make a positive mark in Washington — a message that could remain consistent from the primary to the general election.

"I'm not going to waste my time," if elected, Braun told NBC News. If he can't make a dent, he pledged, "I'm going to head back to Hoosierland."

Braun has raised his profile to the point that with 45 percent still undecided in the only public poll taken, he led on April 11 with 26 percent, to Rokita's 16 percent and Messer's 13 percent. Veteran political observers here say that the combination of Braun's ad blitz, and the relatively sleepy and low-dollar campaigns of his rivals, has vaulted him to front-runner status. But they also say the race is unsettled.

"This is fascinatingly close," said former Rep. Mark Souder, R-Ind. "People who are following are changing their minds. I've never seen such fluidity before."

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In 2017, the American Conservative Union scored 25 votes by House members. Rokita voted with the group, which runs the annual Conservative Political Action Conference in the Washington area, all 25 times. Messer strayed just once, by voting to fund the Manufacturing Extension Partnership, a federal program that shares costs with local governments and private investors to aid small and mid-size manufacturers.

Messer voted for an omnibus spending bill last month that boosted funding for both the military and domestic accounts while Rokita voted against it. But even Trump appeared to be torn on the matter, trashing it publicly before he signed it.

Both lawmakers have had to explain past allegations of driving under the influence. Messer, 49, who won his state House seat after his predecessor was killed by a drunken driver, has been convicted twice on such charges. Rokita, 48, was arrested for illegal consumption of alcohol and possessing a fake ID after a traffic stop when he was in college — the officer reported that he seemed intoxicated — but those charges were dismissed and his campaign has said he passed a sobriety test and was in possession only of closed-container alcohol.

Republican presidential candidate Donald Trump (R) and Indiana Governor Mike Pence (L) wave to the crowd before addressing the crowd during a campaign stop in Westfield, Indiana, 0n July 12, 2016. JOHN SOMMERS II / Reuters

Before Trump was the Republican nominee, Rokita and Messer both bashed him — as "vulgar" and "race-baiting," respectively.

Now, though, they each want to be seen as the logical pick to help Trump advance his agenda in Washington. Messer, who represents portions of the Indianapolis suburbs and the eastern part of the state, notes that he has a slightly higher score (92.9 percent) than Rokita (90.1 percent) in FiveThirtyEight.com's rating of how often lawmakers vote with Trump.

Rokita is also talking like it's still 2016 — referring to "Crooked Hillary" on the campaign trail and keeping alive supporters' calls to "lock her up."

Tina Beck, a Trump backer who voted early for Rokita, lamented last week that Clinton had not yet been jailed, while blasting the media for trying to "get" the president.

Rokita has picked up the endorsement of two leaders of Trump's 2016 campaign in the state, but, in an embarrassing episode, Trump's re-election campaign pressured him to take down signs for implying that Trump was backing him. The president has not endorsed in the primary, nor has Pence, the former Indiana governor.

Matt Gelinske, who owns the House of Thunder Bike shop in Gnaw Bone, about an hour's ride south of Indianapolis, remains undecided, too. But he described his decision process in much the way he explained his support for Trump, whose "America First" policies he likes and whose tax cut just helped him buy a Ford F-250 truck.

"Every candidate is flawed," said the 50-year-old Gelinske. "It's just a matter of which flaws you're willing to look over."

What about Donnelly?

Republicans lost the seat six years ago by nominating archconservative Richard Mourdock over six-term incumbent Richard Lugar. At a debate a couple of weeks before the election, Mourdock said that "it's something God intended" when pregnancies result from rape.

That helped hand the seat to Donnelly, 62, who is among the GOP's top targets this election cycle, and it is reason enough for Republican voters here to be wary of an outsider candidate with little experience in the spotlight for a marquee race for federal office.

Sen. Joe Donnelly (D-IN) speaks at "Making AIDS History: A Roadmap for Ending the Epidemic" at the Hart Senate Building on June 14, 2017 in Washington, DC. Paul Morigi / Getty Images file

While outside groups are dumping several million dollars into attacking and defending Donnelly on the air in Indiana, the senator has been husbanding his own campaign resources — he has about $6.2 million on hand — and waiting for Republicans to sort out who he will face.

"Whoever emerges next Tuesday to face Joe will be bloodied and bruised after a year of nasty personal attacks and millions of dollars of negative ads defining them," said Donnelly spokesman Will Baskin-Gerwitz. "None of these candidates has a positive message for Hoosiers, and none of them can compete with Joe's years of hard work delivering results for Indiana."

For all the personal vitriol in the Republican primary, there's very little venom aimed at the mild-mannered Donnelly, who simply isn't very polarizing. The biggest knock against him is that he's out of step with the state's conservative electorate.

Donnelly has been among the Democrats most likely to vote with Trump — about 55 percent of the time — and, notably, was one of just three Democrats who supported Neil Gorsuch's nomination to the Supreme Court, although he opposed Trump's tax cut and repealing Obamacare.

Trump has been less critical of Donnelly, who does not face a primary challenge, than other Democrats in tough Senate races — namely Claire McCaskill of Missouri, Jon Tester of Montana and Joe Manchin of West Virginia — who have all been targeted by the president in vituperative tweets or public statements.

The stretch run

It's Rokita and Messer who have to make up ground in the closing days of the campaign. Both say they're better bets in November.

Rokita is embarking on a final sprint through 50 events, and his spokesman, Nathan Brand, said that push and the record he has in Congress will help put him over the top.

"Todd will continue to outwork his competition over the final days, talking directly to voters about the need for a pro-Trump, pro-life, pro-Second Amendment conservative who will stand up against the liberal elites in Washington," Brand said.

Brad Todd, a consultant to Messer's campaign, said Republicans need to put up a nominee in November who can win over swing voters in the Indianapolis suburbs.

He said honesty could be the key to the race.

"The whole argument against Donnelly is that in Washington he isn't who he says he is in Indiana," Todd said. "Braun has faced criticism for claiming to be a 'lifelong Republican' in his ads while his voter records show he was a lifelong Democrat even into the Obama years. Rokita claims to have Trump's endorsement but the president demanded he cease and desist. Luke [Messer] heads into the general with the strongest argument against Joe."

Voters here will welcome the end of the ugliness in eight days.

"I wish they'd talk about the issues, not each other," said Cynthia Schrodt, 62, an undecided Republican voter.