So how did Cruz win them over? By putting together a shrewd electoral strategy that thwarted what political scientists call the “public choice” dynamic.

Under this dynamic, policies whose benefits go to a small group but whose costs are dispersed across a large population are hard to undo even when the net costs are greater than the net benefits. Why? Because the beneficiaries have every incentive to mobilize — lobby candidates, influence the media, go the polls — on behalf of the policy. However, ordinary folks don’t have an equal incentive to oppose it because the cost to them is too small to be worth the effort. This problem is even more pronounced in a caucus state like Iowa where voting in the primary is not just a simple matter of pulling a lever but an evening-long commitment.

But Cruz got his supporters to make the schlep on his behalf not by talking them into an anti-ethanol revolt. (A Des Moines Register survey just before the election found that 42 percent of Iowans disagreed with Cruz on ethanol, 37 percent agreed and the rest were undecided, hardly an electorate champing at the bit to send Big Ethanol a message.) Rather, Cruz assembled a broad but piecemeal coalition of conservative voters by giving each faction something it really, really cared about. He wasn’t like McCain, the other anti-ethanol Republican, who threw down the gauntlet to voters and basically told them to take it or leave it.