One year ago, the political experts were sure of two things about Georgia voters: They would deliver the state’s electoral votes to the Republican presidential nominee, and they would reelect Sen. Johnny Isakson to a third term.

Twelve months later, things look very different. Recent polls show Democrat Hillary Clinton is either tied or slightly ahead of Republican Donald Trump. Some of the poll analysts are starting to nudge Georgia into the “Leans Democratic” column. Those same polls also show that the senate race is much closer than expected, with Isakson only holding a single-digit lead over Democrat Jim Barksdale.

The senator is one of the best-known names in state politics and has support from prominent Democrats like U.S. Rep. David Scott, former Gov. Roy Barnes and former Sen. Sam Nunn.

“I’ve always voted for Johnny Isakson," Scott said. "He’s my friend. He’s my partner, and I always look out for my partners.”

But Isakson was expected to be piling up a bigger lead by now. Barksdale entered the race unknown to probably 99 percent of Georgia's voters. He hasn't brought in many contributions, although he has been able to put $3 million in personal funds into the campaign.

The last time Isakson ran for reelection in 2010, he had a credible Democratic opponent in Mike Thurmond, a good campaigner with a decent record as the state’s labor commissioner. Isakson clobbered Thurmond by a 58-39 percent margin. If Isakson could beat Thurmond by 19 points, he should be 20 or 25 points ahead of an opponent who’s never run for office before—but he’s not.

The only factor that really explains Isakson’s wobbly position is the presence of Trump at the top of the Republican ticket. Trump’s erratic behavior since the national conventions is dragging down Republican incumbents everywhere.

New Hampshire is a good example. Clinton had been holding a three or four point lead over Trump, while Republican Sen. Kelly Ayotte held a small lead over Democratic Gov. Maggie Hassan in the Senate race. As the Trump campaign imploded, however, a new poll last week showed Clinton expanding her New Hampshire lead over Trump to 17 points, while Hassan pushed out to a 10-point lead over Ayotte, a Trump supporter.

Similar dynamics are probably at play here in Georgia, especially among independents who might normally vote for a Republican but are turned off by Trump’s antics.

Isakson is a smart enough politician to know that Trump can be poison to down-ballot candidates. When they have been asked about presidential endorsements this year, Isakson and his spokespeople have always been careful to say that the senator will “support the ticket” in November, but they won’t say Trump’s name.

That strategy was evident during a recent campaign swing in Cobb County, where Isakson was asked by a local reporter if he had endorsed Trump yet. This was his answer: “I think it’s important to be for your ticket. If you’re an elected Republican, I think you have an obligation to be for your ticket. That doesn’t mean you’re blindly for your ticket, but it means you’re supportive of your ticket and you’re supportive of your party.” Nowhere in that thicket of verbiage will you find the words “Donald” or “Trump.”

Isakson does have health issues to deal with as he runs for a third term. He is nearly 72 and disclosed last year that he had been suffering from Parkinson's disease, a degenerative disorder of the central nervous system, since 2013. With enough money—Isakson has raised more than $6 million—and an obscure opponent, those kinds of issues can usually be overcome. But when you’ve got a train wreck like Donald Trump at the top of your ticket dragging everybody down, that can make things a lot tougher.