As of Tuesday evening, Brindisi was beating Tenney by more than 4,000 votes after additional absentee ballots were counted. About 1,900 ballots remain to be tallied.
Tenney has not conceded. A winner won’t be declared until state election officials certify the final results.
Brindisi is a 39-year-old lawyer and state assemblyman who campaigned on calls for civility.
The district in central New York supported President Donald Trump in 2016.
Indicted Republican U.S. Rep. Chris Collins has declared victory, saying a count of absentee ballots preserved his lead over Democratic challenger Nate McMurray.
A Collins spokeswoman said in a statement Tuesday that Collins maintained his election night win through the canvass of outstanding ballots. Collins led by 3,000 votes Nov. 6, but the race was considered too close to call.
After the last of the absentee ballots were tallied Tuesday, Erie County elections officials said it was “mathematically improbable” for McMurray to win, despite outstanding affidavit ballots.
McMurray’s campaign didn’t immediately comment. The Associated Press has not called the race.
Collins pleaded not guilty in August to leaking information about a biopharmaceutical company that allowed his son and others to avoid huge stock losses. His trial is scheduled for February 2020.