One thing has become clear about the midterm elections, which will determine the political script for the rest of President Trump’s term: Pennsylvania is where much of the action will be.

Democrats eager to take control of the House of Representatives see rich opportunities in Pennsylvania to pry seats from Republican hands. Swarms of candidates have filed to run in the state’s primary on May 15. And polling data published on Thursday showed strong advantages for the Democrats, in a swing state where Republicans have had the upper hand in recent years.

Two developments are converging to give Pennsylvania its outsize role: New congressional districts drawn by the State Supreme Court make the map more of an equal playing field; and a special-election upset by a Democrat in one of the reddest parts of the state signaled an incipient blue wave.

Democrats appear to be in position to flip at least three, and perhaps as many as six, of Pennsylvania’s 18 House seats, according to strategists from both parties. That could represent a quarter of the 24-seat gain they need nationwide to take control of the House.