In Governor Perry’s then-unambiguous view, the federal law has done “significant harm” to American households. “Any government mandate that artificially props up a single industry to the detriment of millions of Americans is bad public policy,” he said.

But when Mr. Perry, as a Republican presidential candidate, was asked about the ethanol mandate at an Iowa Corn Growers Association meeting in late August, he ducked the issue and would not answer questions. His evasiveness did not sit well with farmers, but the association’s chief lobbyist, Mindy Larsen Poldberg, was somewhat encouraged.

“He didn’t say, ‘No, I don’t support it,’ or ‘Yes, I would support it,’ ” she said. “I wouldn’t say that right now he is against ethanol.”

It remains unclear whether Mr. Perry still opposes the ethanol mandate and was merely avoiding a politically awkward issue, or whether he might have been carving out room to change his position.