Democrats are seeing a groundswell of enthusiasm on the left, but that same energy could complicate the calculus in swing seats and districts carried by Trump that Democrats need to take back the House.

The party will likely need to strike a delicate balance between finding moderate candidates who best match the political profiles of the target districts on issues such as abortion and gun control without alienating its left wing.

“I think it may be helpful in some of the deep red districts or red-of-center districts to have some candidates who may be anti-abortion rights or pro-gun, maybe … more conservative side of some of these social issues,” said Kyle Kondik, the managing editor of campaign analysis site Sabato’s Crystal Ball.