Democrat Katie Porter has taken a 261-vote lead on Republican Rep. Mimi Walters in California’s 45th District.

Why it matters: It’s one of several Orange County-based districts where Democrats lead as California continues counting mail-in ballots -- potentially padding the party’s new majority in the House.

Porter is a protégé of Massachusetts Sen. Elizabeth Warren.

Republicans sought to cast her as out of the mainstream in a county that once was a Republican stronghold, but where Hillary Clinton had won several congressional districts held by the GOP -- including the 45th District.

The new numbers mean Democrats now lead in seven out of 10 uncalled House races.