The promise of change has been a powerful force in U.S. presidential campaigns for decades, a reliable appeal to a fundamental yearning in the American electorate. It was central to the candidacies of John F. Kennedy, Ronald Reagan, Barack Obama and Donald Trump.

"Change vs. more of the same” read a hand-scrawled placard posted on a wall in the campaign war room for Bill Clinton when he captured the White House in 1992.

Yet this year, Americans, who by nearly every measure are hungering for a new direction, are confronted with the choice between a continuation or a restoration.