The back-and-forth between ethanol and oil interests didn’t end with the Iowa caucuses, with both sides claiming victory for their influence over candidates and voters.

The national narrative was that Sen. Ted Cruz’s victory in the Iowa Republican caucus showed the waning importance of the Renewable Fuels Standard (RFS) among Iowa voters.

But pro-ethanol candidates act­ually garnered more support in this year’s caucus than they did in 2012, noted Iowa...