The 12th Amendment says that in that case, the House of Representatives elects the president and the Senate elects the vice president. The new Congress that enters in January is the one tasked with carrying out the so-called “contingent election.” The president has only been selected this way once, in 1825. The winner was John Quincy Adams.
In a contingent election, House members have to choose among the three people with the most electoral votes. Each state delegation gets one vote, and 26 votes are required to win. In the Senate, the choice is between the top two electoral vote-getters and each senator gets a vote, with 51 votes required to win.
What if that fails and the House hasn't elected a president by Inauguration Day? Then the 20th Amendment takes over. It says the vice president-elect acts as president until a president is picked. And if there's no vice president selected by Inauguration Day?
Well, then the Presidential Succession Act applies.
It says that the speaker of the House of Representatives, the Senate president or a Cabinet officer, in that order, would act as president until there's a president or vice president.
Vision 2020 is a new series from the AP dedicated to answering commonly asked questions from our audience about the 2020 U.S. presidential election.