In 2008, the caucuses were held on Jan. 3, when most college students were home on winter break. That meant that Obama's army of young supporters could caucus at their parents' homes all over the state, and not waste their support in Johnson or Story counties, home to the University of Iowa and Iowa State University, respectively.

The Sanders campaign is working to encourage college students to return home to caucus, and helping to arrange travel. But it's a big organizational lift and asking a lot of a demographic that has historically already been reluctant to turn out. The caucuses are on a Monday night, so students will have classes on the day of the caucuses and the next morning.

"I still think HRC by 5 in Iowa," Mitch Stewart, who was Obama's director of field operations for the Iowa Caucuses in 2008 and now backs Clinton, said in a tweet Saturday.