American politics is a broken horror, particularly at the national level, not because politicians are too dirty, but because they’re not nearly dirty enough. Children need to eat dirt to develop immunological resistance that protects them from allergies and disease as they grow up. Something similar is true in politics: Minor forms of corruption—votes bought with earmarks, traded favors—create a political flexibility that keeps the entire system from collapsing in moments of crisis.

But excessive hygiene is rampant in Washington. The controlling conservative wing of the Republican Party is addicted to principle. If politics is the art of compromise, we have a huge number of elected officials who are not politicians at all but rather zealots animated by ideology. This consistency, so admirable in a campaign ad, makes governing and legislation nearly impossible.

A case in point is the House ban on earmarks, a proud achievement of the Boehner majority for the past four years. Grubby and inefficient, earmarks decorate the country with misplaced bridges and idiotic museums. But evidence suggests they also make political compromises possible. The less than 1 percent of federal spending that went to earmarks bought goodwill and dealmaking that lubricated Washington. Earmarks—a bribe, essentially—gave politicians cover to vote against their political interests, in support of someone else’s agenda.