Democratic U.S. Rep. Yadira Caraveo clung to a razor-thin lead over her Republican challenger, state Rep. Gabe Evans, in Colorado’s tossup 8th Congressional District, according to partial, unofficial returns.

With tens of thousands of ballots left to be counted late Thursday, Caraveo led Evans by 2,360 votes, or 0.8 percentage points — close to her narrow margin of victory two years ago, when the nearly evenly divided district was created.

A pair of third-party candidates trailed with about 1% apiece.

Stretching from the Adams County suburbs on the north side of Denver to Greeley in Weld County, the district has been home to one of the most competitive — and expensive — House races in the country since it was drawn following the 2020 census.

After winning the seat by just over 1,600 votes in 2022, Caraveo, a pediatrician and the first Latina to represent Colorado in Congress, faced a challenge from Evans, a military veteran and former police officer serving his first term in the legislature.

The seat is considered crucial to determining which party controls the U.S. House of Representatives. Both sides spent heavily, pouring more than $20 million into a near-constant barrage of mostly negative TV and digital ads and mailers, though campaign finance reports show the Democrats and their allies outspent the Republicans and theirs.

Heading into the November election, Republicans held a slim seven-seat majority in the House, meaning Democrats would have to flip four seats to take the gavel next year. By Thursday night, 21 House races had yet to be called.

The contest was the only Colorado House race rated as a toss-up by national election analysts, and scant polling in the district indicated it was a dead-even race. A poll released a month ahead of Election Day showed the candidates tied, with each at 44%, while a survey conducted by the same firm at the end of October found Caraveo with a 48% to 46% lead over Evans, within the poll’s margin of error.

In the blizzard of ads that flooded screens and mailboxes since Labor Day, Democrats attacked Evans over his positions on abortion rights, while Republicans attempted to saddle Caraveo with concerns surrounding immigration and crime.

Caraveo and Democratic-aligned groups spent millions calling Evans “too extreme” for Colorado, repeatedly focusing on his support for the Supreme Court decision that overturned Roe v. Wade and highlighting comments he made as a teenager opposed to same-sex marriage, before it was legalized in another Supreme Court decision.

Other ads run by Caraveo and her Democratic allies lump Evans in with U.S. Rep. Lauren Boebert and other GOP figures, including Donald Trump, who endorsed Evans.

At the same time, Evans and his fellow Republicans blasted Caraveo for “making things worse,” linking her to the border crisis, crime and the flood of fentanyl into the state. Some of the GOP’s ads pictured the Democrat alongside President Joe Biden, Vice President Kamala Harris and former House Speaker Nancy Pelosi.

Underlining the importance of the race on the national map, Republican and Democratic House leaders campaigned with the candidates multiple times, including recent visits from House Speaker Mike Johnson, a Louisiana Republican, and House Minority Leader Hakeem Jeffries, a New York Democrat, respectively.

Caraveo, the incumbent, outraised and outspent Evans, according to campaign finance filings. Through Oct. 16, the Democrat reported raising $7.3 million and spending nearly $6 million, leaving $1.3 million in her campaign’s bank account. That compares to $2.3 million raised by Evans, who spent $1.9 million and had $363,000 heading into the campaign’s final weeks.

In a first for a Colorado congressional race, both candidates are Hispanic and count Mexican immigrants among their forbearers — her parents and his grandparents. The district was drawn to include the highest share of Hispanic residents of any House seat in the state, making up roughly 40% of its population and a somewhat smaller share of the electorate.

Evans hopes to benefit from an endorsement from the district’s former Libertarian nominee, who dropped out and threw his support behind the Republican after Evans signed on to a pledge to adhere to a number of principles drawn up by the minor party’s leaders.

The move was meant to prevent the Libertarian from siphoning off votes from Evans, under the theory that the conservative-leaning third party can cost Republicans the election in extremely close races.

Colorado’s GOP said that’s what happened two years ago when the Libertarian candidate received about 4% of the vote in the 8th CD race — about twice what the party’s candidates typically draw — while Caraveo defeated Republican Barb Kirkmeyer with a margin of less than 1%.