The marquee primary in Tennessee on Thursday is a 28-year-old former Mitt Romney aide’s attempt to unseat scandal-plagued Rep. Scott DesJarlais.

Grant Starrett is running an aggressive ground game, giving some Republicans hope that he can knock off the three-term Republican in the state’s 4th District.

It’s been almost four years since revelations broke that DesJarlais, the self-described “pro-life” congressman, encouraged his then-wife and a mistress to have abortions. And he’s survived a primary since. But not by much — he won in a 2014 recount by just 38 votes against a less aggressive opponent than Starrett.

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In the open 8th District, whoever wins the GOP primary on Thursday is likely to be the next member of Congress from the reliably Republican district.

Three-term Rep. Stephen Fincher made a name for himself in Washington by pushing for reauthorization of the Export-Import Bank when many in his party wanted to let the export credit agency die. Fincher is leaving Congress at the end of this term, leaving behind a crowded primary field to replace him in his western Tennessee district.

“Nobody seems to really have a good idea,” said one Republican with ties to the state when asked how the 13 candidates would stack on Election Day.

Among the 13 hopefuls, though, there are a handful of front-runners. There’s not much ideological room among them, so the winner will likely be whoever has been able to make the biggest name for himself.

Former Shelby County Commissioner George Flinn has name recognition in the area because he’s run for office before. He ran for this seat six years ago, finishing third in the GOP primary won by Fincher. More notably, in 2014, he challenged Sen. Lamar Alexander, who crushed him in the primary. Two years earlier, he ran in the Memphis-based 9th District seat against Democrat Steve Cohen and lost by a wide margin. 

Besides previous ballot exposure, Flinn also has money on his side — his own. He’s loaned his campaign $2.7 million. But he only raised $45 during the two-week, pre-primary reporting period that ended on July 15.

State Sen. Brian Kelsey has been an early favorite and has raised the most money during the pre-primary reporting period. In his late 30s now, he was first elected to the state legislature at 26. Former Pennsylvania Sen. Rick Santorum campaigned for Kelsey earlier this week saying he was the “proven conservative” in the race.

Former Arkansas Gov. Mike Huckabee has hit the trail for former U.S. Attorney David Kustoff, who has loaned his campaign $106,000 and raised slightly less than Kelsey during the pre-primary reporting period.

Shelby County Mayor Mark Luttrell is the most moderate of the group leading the pack. He was thought to be an early front-runner but hasn’t run the campaign some Republicans expected him to, and raised only $16,000 during the pre-primary reporting period.

With so many contenders, the percent of the vote required to win will likely be low. It’s a similar situation to the open race in North Carolina’s 13th District, where the Club for Growth-backed candidate won a 17-person primary with less than 40 percent of the vote.

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In the 6th District, three-term Rep. Diane Black is facing a primary challenge from perennial candidate Joe Carr, a tea party-backed former state representative. Carr fell 9 points shy of defeating Alexander in the 2014 Senate primary.

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Carr has only spent about $92,000 during the course of the primary campaign, while Black has been taking the challenge seriously. Her campaign has spent about $1.7 million, with about $500,000 alone on TV ads. Black is widely thought to be laying the groundwork for a 2018 gubernatorial bid.