In the heady days of the early 1960s, Democrats began to flirt with the idea of enduring partisan dominance, fancying themselves a permanent majority. Daniel Patrick Moynihan, who had both been a Kennedy and Johnson aide and shared in the headiness of the moment, later welcomed the Republican advances in the 1966 midterms. Several pro-civil rights members of the GOP were elected, and Moynihan also thought Democrats could use the chastening. He later wrote: “There had been much talk of the United States moving toward a ‘one and one-half party system,’ with the Democrats permanently in office and the Republicans a kind of Whig or Federalist remnant. That would have been bad for Republicans and worse for Democrats.”

Susan McWilliams Barndt’s deeply incisive essay this morning reminded me of Moynihan’s reflection. Susan’s compelling case is that a GOP that does not believe it can prevail by normal political means has an incentive to work outside healthy political channels. I would add this by way of addition, not refutation: That holds equally for a Democratic Party that does not believe its conservative opposition is credible.

Given the relatively narrow partisan divisions in the nation, we are a considerable distance from the enduring single-party dominance Moynihan feared. But it is worth revisiting why, as a liberal, he feared it: Democrats who were not challenged would become intellectually lethargic. Moynihan also wrote of this period: “‘For too long, as Lionel Trilling had foreseen and feared, the tenets of progressive government had been exempt from serious external or internal pressure. They had become overassertive and underexamined. Things were promised that could not be delivered.’”

I wholly endorse Susan’s premise and commend her essay. Moynihan also reminds us that, in both directions, viable opposition is as important for intellectual as for political health.