Voters in Kansas 4th Congressional District headed to the polls on Tuesday in an unexpectedly close race. And going into the day, there appeared to be a chance they would send President Donald Trump a rebuke in the first federal election since he won the White House in November.

In the end, Ron Estes, the Republican state treasurer defeated Democrat James Thompson, but early voting numbers showed more enthusiasm than usual among Democrats . Perhaps emboldened by this as the election approached, Thompson openly embraced support from a group that Sen. Bernie Sanders (I-Vt.) backs.

Conceding defeat, Thompson vowed from the stage that he would run against Estes again in 2018.

The contest was over the seat formerly held by Mike Pompeo, the tea party congressman Trump picked to run the CIA. Republicans have a considerable advantage in the district, which is home to Koch Industries, as Pompeo was re-elected by over 31 points in November .

Despite the assumed GOP advantage, Thompson, a civil rights attorney and Army veteran, had raised about $240,000 in small donations, much of which came in the waning days of the race.