Democrat Caleb Frostman, the former head of the Door County Economic Development Corporation, outlasted state Assemblyman Andre Jacque (R) in Wisconsin's 1st Senate district. With most precincts reporting, Frostman led Jacque by a margin of 52 percent to 48 percent.

Frostman's win marks the 25th Republican-held district that Democrats have won in special elections since President Trump was inaugurated in 2017. The party also claimed 19 seats in regularly scheduled elections in Virginia and New Jersey last year, bringing their total red-to-blue flips to 45.

In the same time period, Republicans have flipped just five seats from blue to red.

The Wisconsin district came open when Gov. Scott Walker (R) appointed the previous incumbent, state Sen. Frank Lasse (R), to a job in his administration.

Republicans on Tuesday appeared likely to maintain control of another open seat, this one an Assembly district near Madison, where the GOP candidate had a healthy lead over his Democratic challenger.

Trump won that district by a 14-point margin.

Walker initially declined to call a special election to fill the two seats. But two courts ruled in March that Walker had an obligation to call special elections to fill the seats, even though the state legislature is unlikely to return to session this year.

Democrats accused Walker of shirking his duty to call a special election because he was afraid of further Republican losses. Democrats won a special election earlier this year to fill an open state Senate district, and they won a closely-watched race for a state Supreme Court seat that both sides spent heavily to protect.

"Caleb [Frostman] will be a fierce advocate for Wisconsinites in SD-1, who have gone months without representation because Scott Walker was afraid of more Republican losses after the victories of Sen. Patty Schachtner and Judge Rebecca Dallet," Wisconsin Democratic Party Chairwoman Martha Laning said in a statement. "We can’t forget that Scott Walker selfishly tried to prevent tonight’s elections from happening. Intimidated by the mounting enthusiasm from Wisconsin Democrats, Walker tried to keep these two seats empty and without representation for over a year."

Republicans will maintain control of the state Senate, but by a margin of just two seats. Democrats hope to reclaim control of the state Senate in November's midterm elections.