In this Oct. 7, 2015 file photo, Democratic presidential candidate Hillary Rodham Clinton speaks in Council Bluffs, Iowa.
In this photo taken Oct. 3, 2015, Democratic presidential candidate, Sen. Bernie Sanders, I-Vt, speaks during a campaign rally in Springfield, Mass. The state where Hillary Clinton and Sanders will meet to debate on Tuesday, Oct. 13, for the first time is evidence of why she's still the front-runner. Clinton has staff organizing on the ground for months in Nevada and they know how to navigate the state's baroque caucus system. (AP Photo/Michael Dwyer) Michael DwyerAP
Former Virginia Sen. Jim Webb speaks at an event at the public library in Council Bluffs, Iowa, Thursday, April 9, 2015. Jim Webb and Martin O'Malley are both in Iowa, trying to establish themselves as the alternative to Hillary Rodham Clinton. (AP Photo/Nati Harnik) Nati HarnikAP