For Sen. Bernie Sanders, victory in Iowa's kickoff presidential caucuses hinges on a simple proposition: that his message of political revolution will inspire people who typically stay home on that deep-winter night. Of course, that's easier said than done.

Getting new people out to these party organizing events, which usually draw small numbers, remains the holy grail of Iowa politics.

"We have to reach out to first-time caucus goers or caucus goers who haven't caucused in a long time," said Pete D'Alessandro, who is running the Iowa operation for the Democratic contender.

But while Sanders' campaign message - with pledges of paid family leave, free public university, and single-payer health care - has been received with enthusiasm, he lags behind Clinton in state polls.

Undaunted, a passionate force of staffers is working toward a Sanders victory on caucus night, Feb. 1. - AP