U.S. Sen. Johnny Isakson clobbered two little-known Republican challengers Tuesday in his quest for a third term, while Democratic newcomer Jim Barksdale avoided a runoff against a pair of rivals in his first electoral test.

Isakson won more than three-quarters of the vote over MARTA engineer Derrick Grayson and college professor Mary Kay Bacallao, who both tried to outflank him on the right.

Barksdale, a millionaire investment manager recruited by party leaders, defeated project manager Cheryl Copeland and businessman John Coyne in his contest. He had the edge in the race after pumping more than $1 million into his campaign to fund ads casting himself as an outsider, but Copeland — who raised less than $10,000 — proved a surprisingly strong challenger.

Anything short of a majority on Tuesday would have been a letdown for Barksdale's campaign, since a July 26 runoff would follow.

Isakson is heavily favored to win in November. The 71-year-old helped build the Georgia GOP and scared off big-name Republican and Democratic challengers with a campaign war chest that hovers around $6 million.

But Democrats hope Barksdale, handpicked by party leaders, can flip the script against Isakson. He’s trying to position himself as an outsider who can pump millions into his campaign, much like former Fortune 500 executive David Perdue did in 2014 when he won an open U.S. Senate seat.

Libertarian Allen Buckley, who forced a runoff in the 2008 Senate race, is also running.

Isakson, 71, announced shortly after the 2014 election that he would seek a third term in the U.S. Senate, and he quickly rallied the state’s Republican establishment around him.

That party unity didn’t fray after he revealed last year that he had Parkinson’s disease, and Isakson and his physicians said the illness shouldn’t prevent him from serving another six years.

He easily put away his two Republican opponents Tuesday, but the prospect of a general election against a well-financed political novice presents a different sort of challenge. The veteran politico’s name will be under Donald Trump’s on the November ballot, and some Republicans worry billionaire presidential candidate could hurt the entire ticket.

“Everybody that makes any predictions right now at that question is guessing,” Isakson said shortly after his primary victory. “I have a hunch that there’s going to be a huge turnout this November, and it’s going to be a close horse race. And it’s going to be fun to watch and fun to be in. The results are going to be the best for the people in the country.”

Barksdale, 63, emerged as the Democratic Party's go-to candidate after a string of better-known candidates turned down a chance to challenge Isakson. His campaign had a shaky start, with the candidate dodging public appearances for nearly a month and netting paltry fundraising numbers.

But he's pumped $1.1 million of his own fortune into the campaign, and he used a chunk of that money to finance an advertising blitz across the state. Each prominently features Barksdale's gray cap, which he declares in one ad marks him as an "outsider."

“I’m not a politician. I had never even thought about doing something like this. I haven’t lived a political life, and I haven’t been out on the political front,” Barksdale said in an earlier interview, adding: “But I’ve had so much given to me that I didn’t deserve, and I have a responsibility to give back.”

Isakson, for his part, said he wouldn’t let Trump or a Democratic opponent change his game plan, which mixes his conservative credentials with a willingness to reach out to the left.

“I respect every opponent I’ve ever had,” Isakson said. “But I’m going to make sure I run the race I want to run.”