Democrat Anthony Brindisi is projected to defeat Republican Rep. Claudia Tenney in New York's 22nd District, according to NBC News.
The race has been tight since the outset, even though President Donald Trump won the district by 20 percentage points during the 2016 presidential election.
While most polls had Brindisi in the lead, Tenney was often behind by just the margin of error. Nonpartisan political analysis site Larry Sabato's Crystal Ball labeled the district a toss-up.
NBC News has projected that the Democrats would take back the House.
The Republican incumbent ran a campaign that was in lockstep with the president.
Trump in August made the first presidential visit to Utica in about seven decades, praising Tenney. "I'm here for Claudia. She has been incredible in Congress. She has helped us so much," he said. "Hopefully we put Claudia right over the top where she belongs."
Since Trump overwhelmingly won the district two years ago, Brindisi was forced to walk a tightrope in order to not offend those who backed the president. For instance, he has been hesitant to criticize Trump's Supreme Court nominee Judge Brett Kavanaugh even after the judge was accused of sexual misconduct.
However, the Democratic assemblyman has been critical of Trump's trade war, arguing it hurts dairy farmers in the district.
Voters were inundated by attack ads from outside groups, making it one of the most expensive congressional races of the midterms. Outside political committees spent $13 million on the race, according to the nonpartisan Center for Responsive Politics.