Frankie Giardino, 5, plays with a pom-pom as he awaits the arrival of his uncle David Kustoff at Marriott Memphis East on Thursday, Aug. 4, 2016. The candidates who have spent the heaviest on the race for the GOP nomination for the 8th District seat include radio station owner George Flinn, businessman Brad Greer, state Sen. Brian Kelsey, former U.S. Attorney Kustoff and Shelby County Mayor Mark Luttrell.

COLLIERVILLE, Tenn. — Former U.S. attorney David Kustoff outpaced a crowded field of Republicans vying to be the party's nominee for an open west Tennessee congressional seat Thursday.

Meanwhile, incumbents Scott DesJarlais and Diane Black won the GOP nomination in the 4th and 6th districts, respectively. U.S. Reps. Chuck Fleischmann and Phil Roe also won the Republican primaries in their congressional districts.

In the 9th District, Democrat U.S. Rep. Steve Cohen easily won his party's primary.

Kustoff beat radiologist and radio station owner George Flinn in the 8th District primary. In all, 13 GOP candidates jumped into the race after the surprise announcement that U.S. Rep. Steve Fincher would vacate his heavily Republican seat after three terms.

Other leading candidates who sought to replace Fincher included state Sen. Brian Kelsey, Shelby County Mayor Mark Luttrell and businessman Brad Greer. All are from the Memphis area except for Greer, who is from Jackson. The part suburban, part rural 8th District includes a section of Shelby County and a wide swath of west Tennessee, including the cities of Jackson, Dyersburg and Union City.

Kustoff's tenure as U.S. attorney for the Western District of Tennessee included the prosecution of former state Sen. John Ford and others as part of the Tennessee Waltz political corruption case. Kustoff also won an endorsement from former Arkansas governor and presidential hopeful Mike Huckabee, who has support among conservatives in Tennessee.

"If Mike Huckabee endorses Kustoff, then he must be the conservative guy that we want, because we definitely want to protect our Second Amendment rights," said voter Don Turner, a 53-year-old systems analyst who voted at a church in Eads.

Kustoff will face Democrat Rickey Hobson in the general election in November.

In another hard-fought congressional primary, Black defeated former state Rep. Joe Carr to gain the Republican nomination for Tennessee's 6th Congressional District. The 6th District runs east from the Nashville suburbs to the Cumberland Plateau.

Black outspent Carr, but the challenger relied heavily on conservative talk radio to attack the incumbent as a member of the "establishment."

Carr surprised many observers by coming within 9 percentage points of defeating U.S. Sen. Lamar Alexander, a former governor and presidential candidate, in the 2014 Senate primary.

Although Alexander largely ignored the Carr campaign during that nomination fight, Black went on the offensive against her challenger this year. Black campaign materials targeted Carr for living outside the district boundaries and for being a perennial candidate.

"It's the only way I know how to run a campaign," Black told WTVF-TV on Thursday evening.

Chad Swan, a vascular and thoracic surgeon, said he was impressed with Black after he contacted her about his concerns when a local hospital went bankrupt.

Bruce Pershke, who said he's a longtime friend of Black's, said he would not have voted for Carr even if she weren't in the race.

"I think he's all politician," Pershke said of Carr. "He's basically looking for a job."

In the 4th District, the scandal-plagued DesJarlais defeated challenger Grant Starrett, a Murfreesboro real estate attorney, for the GOP nomination. The 4th District runs southeast from the suburbs of Nashville to the outskirts of Chattanooga.

DesJarlais, a physician from Jasper, has survived cancer and a series of revelations that included affairs with patients. He also urged a mistress to seek an abortion and once held a gun in his mouth for hours outside his ex-wife's room. He now opposes abortion rights.

"The people of the 4th District know I will always fight for Tennessee values and principles," DesJarlais said in a statement.

Wyndee Clara, a 47-year-old stay-at-home mom from Murfreesboro, said she voted for DesJarlais because he provides good constituent services and keeps voters in the loop about what's happening.

"He's been doing a really good job of communicating," Clara said.

Fleischmann defeated GOP challengers Allan Levene and Geoffrey Smith in the 3rd District, while Roe beat Clint Tribble in the 1st District primary.

This story was updated Aug. 4 at 11:15 p.m. with more information.