NASHVILLE, Tenn. - Early primary voting is under way in Tennessee and election officials expect more than half of all voters who will cast ballots this summer to take advantage of the head start.

The Aug. 5 primary vote will decide the Republican gubernatorial nominee from among Knoxville Mayor Bill Haslam, state Senate Speaker Ron Ramsey and U.S. Rep. Zach Wamp.

Haslam and Ramsey kicked off their day of campaign in Memphis. About 30 people attended a morning Haslam rally that also served as the start of his statewide bus tour.

"We have 20 days - 20 days - until election day," Haslam said. "It is critically important that we sprint to the finish line."

Ken Hall listened to a short speech from Haslam and took photos of the candidate at a later event at the Hard Rock Cafe on Beale Street. He said he planned to vote for Haslam early next week at a community center.

"I like to avoid the big long lines. What if I had a flat tire on Election Day and I couldn't get there or missed it by 30 minutes?" said Hall, a marketing consultant. "By going early, I've ensured that I will get my vote cast."

About 150 people gathered for a Wamp rally in Chattanooga, including his family, supporters who rode on a school bus and his pastor at Red Bank Baptist Church, the Rev. Adam Dooley.

"Even if I wasn't his pastor I'd be voting for Zach Wamp," Dooley said at the rally that started and ended with prayers, included entertainment by a band and a fly-over by a small plane towing a Wamp banner.

Wamp said there is not enough vision in politics and "the Scripture says that where there is no vision people perish."

"We need vision in American politics today," he said.

Wamp said he was undeterred by the fundraising efforts of Haslam, whose $9.1 million total is more than Wamp and Ramsey combined.

Wamp said $5 million "for a good candidate, that's all it's going to take."

"Tennessee, don't let the Haslams buy it," he said.

Dairy equipment retiree Bob Doremus of Chattanooga stood in the sweltering sunshine holding a homemade Wamp campaign sign.

"I believe he is telling the truth," Doremus, 78, said afterward. "He brings out the truth in everything, like the religion in it."

Later Friday, Ramsey received the endorsement of a handful of state legislators at his Memphis campaign office.

"My campaign has peaked at exactly the right time," Ramsey said. "People are just now starting to examine the candidates."

Ramsey said early voting has made campaigns more expensive because it requires getting the message out earlier.

"It's made billionaires like Bill Haslam be more likely to be elected because he has an unlimited amount of funds," Ramsey said.

Gov. Phil Bredesen can't run again because of term limits. Jackson businessman Mike McWherter, son of former Gov. Ned McWherter, is the only Democrat running to succeed him.

McWherter voted Friday in Jackson with his wife Mary Jane and their 18-year-old son Walker, who was casting his first ballot.

The primary will also determine which candidates will matchups for three open congressional seats. Democratic Reps. John Tanner of Union City and Bart Gordon of Murfreesboro are retiring and Wamp is giving up his East Tennessee seat to run for governor.

Another contentious primary is between Democratic Rep. Steve Cohen and former Memphis Mayor Willie Herenton in the 9th District. Both candidates have early voting rallies planned for Saturday.