ATLANTA — Republican Sen. Johnny Isakson insists he won’t be a “volunteer apologist” for Donald Trump or anyone else who utters something stupid, but that defiant independence is being sorely tested by the GOP presidential nominee’s sinking support and Democrat Hillary Clinton’s push into surprisingly competitive Georgia.

The down-ballot Senate race involving the affable, two-term Isakson wasn’t ranked as poachable for Democrats despite the changing demographics in the southern state and the higher, diverse turnout of a presidential election year. After all, reliably Republican Georgia has only voted for a Democratic presidential candidate once since 1980.

That was Bill Clinton in 1992.

Recent polls show Trump and Hillary Clinton locked in a tight race as the Democrat opens a campaign office in the state and invests in a field organization. Isakson holds a single-digit lead over first-time candidate Jim Barksdale, a wealthy investment manager whose opposition to trade deals and calls for a higher minimum wage has attracted backers of Vermont Sen. Bernie Sanders, the unsuccessful Democratic presidential candidate.

The 71-year-old Isakson, who disclosed he has Parkinson’s disease, sought to shore up his support with Republicans while appealing to independents and Democrats. He made a two-day trip around the state in late July to highlight the Georgia Chamber of Congress’ endorsement with low-key stops at large companies in five cities to tour factory floors and talk with employees.

In metro Atlanta recently, Isakson talked about his Senate work to members of a Rotary club, a business group and a Realtors’ association.

Questions about Trump’s more divisive comments proved inevitable. Isakson says he’ll support the GOP ticket but won’t answer for the nominee.

“If Donald Trump or anybody else makes a stupid statement, I’m not going to be their apologist and let the press beat up on me,” Isakson said in an interview with The Associated Press. “They’ll have to go to the person who made the stupid statement. I’ll apologize when I do something stupid because I should. But I’m not going to be the volunteer apologist for anybody else.”

He says he doesn’t expect “a lot of coattails” from either party’s presidential ticket.

Isakson’s supporters, including some still struggling to wholeheartedly support Trump, said they believe the incumbent can go it alone. Ben Hinson, a retired business owner from Macon, said he plans to support Trump because Clinton is the alternative, but he does worry that independents will be driven away from the overall GOP ticket.

“I think Johnny’s stronger in Georgia than any presidential candidate this year,” Hinson, 64, said. “I don’t see any upside to him getting close to Mr. Trump. I think Sen. Isakson can run his race quite on his own.”

With a $4 million cash advantage, his first ad of the general election made a direct pitch to Democrats, focusing on Isakson’s response to the 2009 murder of Georgian Kate Puzey while volunteering in the west African country of Benin for the Peace Corps.