PORTLAND, Maine — In closing days of a bruising midterm election campaign, Democrats are putting Republicans on the defensive in red territory supportive of President Trump, upping their chances of winning the House majority.

Some districts, like Maine’s 2nd, where Democrat Jared Golden is pressing Republican Rep. Bruce Poliquin, have been competitive for months. But a round of late-breaking House seats have emerged in Trump territory that typically delivers easy victories to the GOP, expanding Democratic opportunities for gains and forcing overwhelmed Republicans to stretch precious resources even thinner.