Representative Don Bacon, the five-term Nebraska Republican who represents a centrist district in a deeply red state, will not seek re-election, according to a person familiar with his plans, handing Democrats a prime opportunity to pick up a seat in the closely divided House.

Mr. Bacon’s official announcement is expected on Monday, and his departure is not unexpected. His willingness to publicly disagree with President Trump has made him an anomaly in the tribal House Republican Conference, where members tend to fall in line behind the president’s agenda and rarely criticize him in the open. Democrats and Republicans alike had suspected that Mr. Bacon was heading for the exits.

But the upcoming announcement, which was reported earlier by Punchbowl News, marked a major break for Democrats hoping to win control of the House next year, and with it a foothold for pushing back against Mr. Trump. Republicans control the House with a slim three-vote majority.

The political terrain in Mr. Bacon’s district has been trending to the left, making a re-election more difficult even for a Republican who managed to win a district that both former President Joseph R. Biden Jr. and former Vice President Kamala Harris won by more than four points. Democrats are hoping it will be impossible for a Republican newcomer without Mr. Bacon’s reputation and unique electoral strength in his district.

In May, a Democrat unseated a three-term Republican in the Omaha mayor’s race. The morning after that race was called, Representative Hakeem Jeffries, Democrat of New York and the minority leader, told the House Democratic Caucus that it was officially on “Don Bacon retirement watch,” a statement that was greeted with cheers.

“The writing has been on the wall for months,” said Madison Andrus, a spokeswoman for the Democratic Congressional Campaign Committee. “Don Bacon’s decision to not seek re-election in 2026 is the latest vote of no-confidence for House Republicans and their electoral prospects.”