THROUGHOUT the 2016 primary season, two sentiments took turns reassuring Republicans as they watched Donald Trump’s strange ascent:

At some point, Trump will start behaving normally.

If he doesn’t, he’ll self-destruct or quit — or else somebody in authority will figure out a way to jettison him.

It isn’t surprising that people once believed these things; I clung to the second sentiment myself.

What is surprising is that after everything that’s happened, so many people believe them even now.

The reaction to the sacking of James Comey is the latest illustration. Far too many observers, left and right, persist in being surprised at Trump when nothing about his conduct is surprising, persist in looking for rationality where none is to be found, and persist in believing that some institutional force — party elders or convention delegates, the deep state or an impeachment process — is likely to push him off the stage.

Start with the president’s Republican defenders. Not the cynics and liars, but the well-meaning conservatives who look at something like the Comey firing and assume that there must be a normal method at work, who listen to whatever narrative White House aides spin out and try to take it seriously.