If one looks at a county map of Iowa for the 2008 Democrat caucuses
http://politicalmaps.org/2008-iowa-caucus-election-results-maps/
it can be seen that Obama won a fair number of mostly rural counties. Bernie can repeat that, and probably do more.
As the article describes, it depends on whether Sanders has convinced enough student supporters to leave campus, return to their rural homes and drag their relatives and friends out tonight to caucus.
“....While both parties caucus on the same night, they do so with different rules.
Republicans vote by private ballot. The state’s 30 Republican delegates are awarded proportionally based on the stateside vote.
Democrats take a more interactive approach, with voters forming groups and publicly declaring their support for a candidate. If the number of people in any group is fewer than 15 percent of the total, they can either choose not to participate or can join another viable candidate’s group.
Those numbers are awarded proportionately, based on statewide and congressional district voting, as Iowa Democrats determine their 44 delegates to the national convention....”