Patty Schachtner defeated Republican state Rep. Adam Jarchow for an open state Senate seat Tuesday in an upset victory for struggling Wisconsin Democrats, signaling voter anger toward President Donald Trump that could cost the GOP more legislative seats in the fall elections.

Jarchow tweeted his concession to Schachtner late Tuesday evening, with returns nearly complete across five counties and Schachtner leading by more than 1,600 votes. Schachtner, the St. Croix County medical examiner and a Somerset school board member, had entered the race in northwestern Wisconsin’s traditionally conservative 10th Senate District as the clear underdog.

The district has trended conservative for years. Republican Sheila Harsdorf held the Senate seat for 16 years before she resigned in November to become Gov. Scott Walker’s agriculture secretary and every county in the district voted for Trump in 2016.