Democrats won an exurban St. Louis seat in the Missouri state House of Representatives on Tuesday, racking up another victory in a district carried easily by President Trump in the 2016 election.

Voters in Jefferson County appeared to choose Mike Revis, a 27-year old Democrat, to fill a seat left vacant when the incumbent quit to run for county executive. With all 10 precincts within the district reporting, Revis led Republican David Linton by 108 votes, or about 3 percentage points.

If Revis's lead holds, it would mark a significant swing from 2016, when Trump won the district by a 61 percent to 33 percent margin.

Four years before that, Mitt Romney beat President Obama in the district, south and west of St. Louis, by a 55 percent to 43 percent margin.

Democrats will portray the unexpected win Tuesday as more evidence that the party's voters are fired up ahead of November's midterm elections, after a string of special election wins over the course of the last year.

Revis is the second Democrat this year to win a Republican-held seat in a state legislative race, after Democrat Patty Schachtner won a state Senate seat in Wisconsin.

In 2017, Democrats won 15 special elections in districts previously held by Republicans - including a U.S. Senate seat once held by Attorney General Jeff Sessions, which Sen. Doug Jones (D) won in December.

Republicans easily won two other special elections to fill House vacancies on Tuesday, and the GOP still enjoys a supermajority in the state House.

One more district, a rural seat about halfway between St. Louis and the Arkansas border, remained too close to call as of 10 p.m. EST. In that race, Democrat Jim Scaggs led Republican Chris Dinkins by just 66 votes out of about 4,100 cast, with 10 precincts yet to report. President Trump won that district by an incredible 78 percent to 19 percent margin, making the narrowness of the race even more remarkable.

But the Democratic win is sure to startle Republicans who hope to hold on to control of key legislative seats in suburban and exurban districts around the country.