In normal times, a special election in a congressional district that hasn’t elected a Democrat in more than 40 years wouldn’t be the type of thing that the sitting president would get heavily involved in. But President Trump has made a serious effort over the past few days to encourage voters in Tennessee to back Republican Matt Van Epps on Tuesday in his surprisingly tight race against Democrat Aftyn Behn for a seat in the U.S. House of Representatives.

“The whole world is watching Tennessee right now, and they’re watching the district,” Trump said via speakerphone during a rally in support of Van Epps on Monday morning. “We have to win this seat,” he added.

Trump’s intervention in the special election — which included a plea on social media to “GET OUT AND VOTE” — is a signal of how important the contest is and of how dramatically the political ground has shifted in the span of just over a year.

The GOP has had uninterrupted control of Tennessee’s Seventh District, which includes parts of Nashville and rural areas to the city’s west, since 1983. Last year, the district voted for Trump by more than 20 points and helped GOP incumbent Mark Green win reelection to the House by a similar margin. Green resigned from his seat in July to pursue an opportunity in the private sector he said was “too exciting to pass up.” That set the stage for Tuesday’s special election to fill the vacancy created by his resignation.

It will be the last major head-to-head contest between the two parties of the year in the U.S., and the first since Democrats’ dominant performance in last month’s off-year national elections.

Van Epps, a military veteran and former head of the Tennessee Department of General Services, easily won the Republican primary thanks to endorsements from both Trump and the state’s current governor, Bill Lee. Behn, a member of the state Legislature since 2023, squeaked out a win in an incredibly tight Democratic primary for the chance to face off against Van Epps in the general election.

A recent poll showed Van Epps ahead by just 2%, with enough voters still undecided to tip the race in Behn’s favor.

Whether Behn is able to close the gap by Tuesday or not, the fact that the race is even competitive at all serves as an indication of how much ground Republicans have lost with voters less than a year into Trump’s second term in the White House.

Beyond what it says about the national political climate at the moment, the result of the race will also have a significant practical impact on Congress. Right now, Republicans have a slim 219-213 majority in the House. A win by Behn would make that margin even tighter, leaving House Speaker Mike Johnson with even less margin for error as he navigates a long list of looming legislative challenges — including a late-January deadline to pass a funding bill to prevent another government shutdown.

Pollsters are giving Democrats a strong chance of taking control of the House after next year’s midterms, but a victory on Tuesday in Tennessee could also help set up a scenario in which they may not have to wait that long.

A victory by Behn would shrink the GOP’s advantage in the House to just five seats. The margin is on track to become even smaller in January when Republican Rep. Marjorie Taylor Greene resigns and Democrats elect a new member to fill a vacant seat in Texas. Another special election in New Jersey scheduled for April could leave Republicans with just a two-seat margin, small enough to leave them at risk of surrendering their majority entirely if they lose any more members to retirement or illness.

Given the stakes of Tuesday’s election, money has been pouring into the race in support of both candidates. A Trump-supporting group has spent more than $1 million to back Van Epps. The Democrat-aligned House Majority PAC has spent a similar amount on ads supporting Behn.

Early voting has tilted in Behn’s favor, but Van Epps will have plenty of room to overcome her lead, pollsters say.

“The special election in Tennessee’s Seventh District will come down to what groups are motivated to turnout on election day, and who stays home,” Spencer Kimball, executive director of Emerson College Polling, said last week.