It has become de rigueur to lament the wild proliferation of Republican presidential primary debates. And, as someone who has had to watch all twenty of them, I certainly agree that they can numb the mind.

But they have actually been good for the Republican nomination process. Cast your mind back to last summer. Michele Bachmann surged to the top of the polls when she entered the race, and Rick Perry replicated the feat when he declared his candidacy. Meanwhile, Rick Santorum and Newt Gingrich wallowed near the bottom of the polls. Santorum and Gingrich raised far less money than Perry and were widely dismissed and ignored by the media.

What killed Perry’s candidacy and breathed life into Gingrich’s and Santorum’s? The debates. And that’s a good thing. You might have a hard time imagining worse prospective presidents than Gingrich and Santorum, but such people exist. Three of them are former Republican front runners: Perry, Bachmann and Herman Cain.

Say what you want Santorum and Gingrich—they’re extremists, they’re cruel, they’re corrupt Washington insiders—but they aren’t morons. Gingrich and Santorum are genuinely knowledgeable about policy, and they are capable of stringing together complete sentences in which they articulate their policy agendas.

Cain, Perry and Bachmann were shockingly ill-prepared to lead the free world. Each was more ignorant of basic facts regarding American and international politics and policy than the next. And the debates, which force the candidates to answer questions, not merely deliver memorized stump speeches, is what undid them.

Everyone knows that Perry’s poor debate performances, most especially his painfully embarrassing inability to remember which cabinet departments he proposes to eliminate, destroyed his campaign. But what about Bachmann? Her downfall isn’t explained by any scandal. Perhaps her constant insistence on answering every debate question with an irrelevant talking point failed to impress audiences. It certainly didn’t help.

Likewise Cain’s rote incantation of “9-9-9” grew tiresome. His campaign was damaged more by multiple accusations of infidelity and sexual harassment than his lack of policy knowledge. But his failure to demonstrate sufficient knowledge, especially in international affairs, harmed him as well.

You wouldn’t think that a political movement so proudly anti-intellectual would narrow its presidential field down to its four smartest candidates. But so it has. And we have the debates to thank for that.