Renewable-fuels advocates are promising to spend millions putting ethanol back in the debate for Iowa’s first-in-the-nation caucus next year as cheap oil and setbacks in biofuels policy make the additive less central to voters. Iowa Governor Terry Branstad, backed by state corn-grower and renewable-fuels associations and the Washington-based biofuels lobby Growth Energy, on Thursday formed America’s Renewable Future, to make the Renewable Fuels Standard an issue in the 2016 race. The Iowa caucus is set for early January. “We are designing it to look like a presidential campaign, but the RFS is our candidate,” said Eric Branstad, the governor’s son...