NASHVILLE (AP) - Early voters began casting their ballots Friday for Tennessee's primary election, with tea party-styled challenges to U.S. Sen. Lamar Alexander's bid for the Republican nomination to a third term.

Alexander is looking to avoid an upset from state Rep. Joe Carr of Murfreesboro or Memphis physician and radio station owner George Flinn. Carr has sought to consolidate tea party support, while Flinn has given $1.8 million of his own money into his final push.

Turnout for the Aug. 7 primary is expected to be light. Hard-fought statewide primaries drew about 30 percent of voters in 2006 and 2010, but lower-profile campaigns in 2008 and 2012 drew less than 20 percent of voters. Close to half of all ballots in the last two primaries were cast by early or absentee voters, meaning time is running out to make a case to undecided Republicans.

Alexander, a former two-term governor who also ran for president twice, in a recent inter view noted that he has gained a majority in each of his previous five primary campaigns and that he has campaigned heavily to persuade Republican voters to rally behind him again this time.

"I've focused over the year on staying in touch with Tennesseans and presenting myself as a conservative with an independent streak who knows how to get results," Alexander said. "And if Tennesseans want more of that, why then I'll be re-elected."

Carr has cited the upset tea party win over House Majority Leader Eric Cantor in Virginia as a blueprint for his campaign against Alexander. Conservative talk radio host Laura Ingraham has declared herself "all in for Joe Carr," and plans to campaign on his behalf next week.

Also on the primary ballot are all nine congressional seats, the gubernatorial and state legislative races and retention votes for three state Supreme Court justices.

The GOP primary in the 4th Congressional District pits embattled U.S. Rep. Scott DesJ arlais against state Sen. Jim Tracy of Shelbyville. DesJarlais, a Jasper physician before his election, is seeking a third term despite revelations he had affairs with patients and once urged one of them to seek an abortion.

Tracy has heavily outraised DesJarlais and is counting on voters supporting an alternative to the scandal-plagued incumbent. But DesJarlais has overcome those obstacles before, and some supporters say they want to focus on his record as a congressman rather than on his personal history.

"Sometimes the past is the past, you ought to look beyond it," said Sarah Land, a DesJarlais supporter from Dunlap. "If you looked in a lot of other people's past, there's a lot of people you wouldn't like. You've got to look at what's coming ahead."

In the 3rd District, U.S. Rep. Chuck Fleischmann again faces a challenge from Weston Wamp, the son of a former congressman. Fleischmann, who won the seat vacated by Zach Wamp when he ran for governor in 2010, beat the younger Wamp and dairy executive Scottie Mayfield to win the GOP nomination on his way to a second term in 2012.

In the majority black 9th District centered in Memphis, Rep. Steve Cohen, who is white, is being challenged in the Democratic primary by private attorney Ricky Wilkins and activist Isaac Richmond, both of whom are African-American.

If any sitting House member is defeated, it would be only the second time a Tennessee congressman has seen a primary defeat since 1966. Former U.S. Rep. David Davis was the last incumbent to lose when he was beaten by fellow Republican Phil Roe of Kingsport in 2008.

Gov. Bill Haslam, who faces no serious opposition in the Republican primary, cast his early vote in Knoxville on Friday afternoon.