Driving their concerns are Trump’s approval rating, which has ticked upward in recent weeks, and high Republican turnout in some recent primaries, suggesting the GOP base remains energized. What’s more, Republicans stand to benefit politically from a thriving economy and are choosing formidable candidates to take on vulnerable Democratic senators.

One of their biggest sources of anxiety is the Senate race in Florida, where some Democrats fear that three-term Sen. Bill Nelson has not adequately prepared to defend his seat against Gov. Rick Scott, a well-financed former businessman handpicked for the race by Trump. Scott and Nelson are close in early polls.

“I’m concerned about the race. I think everybody is,” said Ione Townsend, the Democratic Party chair in Hillsborough County, home to Tampa. Townsend said it will “be hard to compete” with Scott’s money.