In just over a year, Americans will vote on which party will control both houses of Congress. President Donald Trump’s Republicans currently control both, but only by narrow majorities (53 to 47 in the Senate and 219 to 213 in the House of Representatives). There is no modern precedent in which a president’s party could avoid losses in midterm elections in the House of Representatives unless his popular approval rating was well above 50 percent, and in Trump’s case, polls show his approval at 45.3 percent while 51.9 percent of voters disapprove of him.