Barack Obama was the president of the United States from 2009 to 2017 (and Donald Trump’s predecessor in that role). During his presidency, the U.S. electorate and political system became more divided and polarized than ever before. Obama tried to encourage unity and reinforce democratic norms of civility and mutual toleration, but his Republican opposition painted him as an illegitimate leader and an existential threat to the American way of life. In response to Republican obstructionism in Congress, Obama also weakened the norm of institutional forbearance—for instance, he governed through an unprecedented number of executive orders.