Representative Leonard Lance, the incumbent in the Seventh District, is highly vulnerable thanks to anti-Trump sentiment, even though he is a moderate Republican who voted against his party’s tax plan and voted to repeal the Affordable Care Act. He isn’t likely to face much trouble from his Republican primary challengers, so the real action on Tuesday is in the Democratic primary, where the former Obama administration official Tom Malinowski is running against Peter Jacob, who lost to Mr. Lance in 2016.