** FILE ** Democratic presidential hopeful New York Sen. Hillary Rodham Clinton talks with research scientist Laura Higgins while touring the Pioneer Hi-Bred International Facility Research Greenhouses in Johnston, Iowa in this March 5, 2007 file photo. At a time when demand for the corn-based fuel is soaring, support for ethanol among candidates is nearly unanimous and has largely crowded out talk of other agriculture-related issues. (AP Photo/Charlie Neibergall, File)