The border-wall tantrum and government shutdown show how Trump has squandered the opportunity that his populist campaign offered. If he had broadened his coalition — using the “art of the deal” he touts but doesn’t seem to understand — he would have presented a more formidable and lasting challenge to the Democratic Party.

But the president’s insecure, all-or-nothing politics has prevented the compromises and horse-trading that might resolve festering problems and, forgive the phrase, make America great again. Instead, we have a paralyzed, dysfunctional government that even Trump enthusiasts must know is bad for our national health. Every additional day Trump sulks in the White House, his failure is more obvious.

The challenge for the Democrats is to avoid Trump’s blunder of creating a headline-grabbing insurgency and, instead, forge a broad governing coalition. That won’t be easy; governing is dull, whereas insurgent movements are sexy. They animate the “base” of true believers and tap the inchoate public anger at the status quo. But insurgencies are self-limiting; they focus inward rather than outward, and are about protesting rather than fixing.