With Donald Trump almost certainly the Republican Party’s candidate for president, pundits in and out of the conservative movement are predicting devastating effects for the party.

They have good reason to think so. Political scientist Stephen Skowronek’s thoughtful theory of presidential leadership suggests that, if Trump were to be elected, his presidency would end the Reagan era. Trump could be such a disastrous president that he would open the way for a transformative Democratic Party candidate to win the presidency in 2020, overcome congressional opposition, and put in place a 21st-century New Deal.

According to Skowronek’s “The Politics Presidents Make,” a president’s political success depends on where he (or, potentially, she) falls in a cycle of party dominance. The 1993 book says that five “reconstructive” presidents have come to office, overthrowing the dominant party and replacing it with their own party: Thomas Jefferson, Andrew Jackson, Abraham Lincoln, Franklin Roosevelt and Ronald Reagan. During these periods, successive presidents of the same party extend those “reconstructive” presidents’ work, while opposing presidents accommodate their winning agenda, as Bill Clinton accommodated the Reagan agenda with his “third way” approach.