As the nation’s capital broiled in the summer heat, the president found himself increasingly isolated in the Oval Office. During his decades in politics, he had charted a career from the Senate to the vice presidency, though after two terms in the nation’s second-highest office, most believed his political career to be over. Even so, he shocked the political establishment by winning the presidency, largely by promising to return a sense of calm following a time of crisis and public protest. Suddenly, however, the president found himself fending off calls from members of his own party to step aside, as...