With all precincts reporting, DesJarlais and challenger Jim Tracy were separated by a 33-vote margin, illustrating the willingness of the incumbent's tea party base to overlook his personal problems that included once urging a mistress to seek an abortion.
The final result of Thursday's election may drag out until the end the month as election officials consider provisional ballots and potential challenges.
In the other high-profile Tennessee primary contest, Republican Lamar Alexander became the latest U.S. senator to fend off a tea party challenge, defeating a state representative who had used a familiar tactic in trying to cast him as an out of touch insider.
Alexander, a former two-term governor, ended up with 49.7 percent of the vote, compared with 40.5 percent for Rep. Joe Carr of Murfreesboro.
In both of DesJarlais' previous elections, he tried to cast doubt on reports of violent behavior toward his ex-wife and about multiple extramarital affairs before his divorce was finalized.
But court transcripts released the week after the November 2012 election revealed that he admitted under oath that he had eight affairs, encouraged a lover to get an abortion and used a gun to intimidate his first wife during an argument.
And last year, DesJarlais, a physician, was fined and reprimanded by the Tennessee Board of Medical Examiners in May for having sex with patients before he was elected.
DesJarlais dismissed those details as "old news," noting that he now is happily re-married while stressing familiar tea party attacks on President Barack Obama over health care and the assault on a U.S. consulate in Benghazi, Libya.
"Tennesseans chose to judge me on my record in Washington," DesJarlais said in a statement.
Tracy, a state senator and former college basketball referee, stressed themes of integrity in his campaign against DesJarlais. That message resonated with some voter's like Linda Warpool of Murfreesboro, who said she was tired of the incumbent's scandals.
"Too much sex. Too many abortions," she said.
But Tracy was unable to persuade enough voters in the more rural counties around DesJarlais' home in the southeastern part of the state, many of which voted overwhelmingly for the incumbent.
In the state's majority black 9th Congressional District, Democratic Rep. Steve Cohen, a white and Jewish Memphis native, defeated attorney Ricky Wilkins. Wilkins, who is African-American.
And in the 3rd District in eastern Tennessee, Rep. Chuck Fleischmann for the second straight primary defeated Weston Wamp, the son of former Rep. Zach Wamp.
Three Democratic members of the Tennessee's Supreme Court survived a concerted effort by conservatives to deny them another eight-year term. Republican Lt. Gov. Ron Ramsey had spearheaded the effort to oust the three justices appointed by then-Gov. Phil Bredesen, a Democrat.
The defeat of even one of the incumbents would have given the GOP control of the highest court in Tennessee, which is the only state in the nation where justices name the attorney general.
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