The latest polls in Iowa show: Trump 24.7% Cruz 22.7% One month ago it was: Trump 25.0% Cruz 11.0% Obviously Cruz is trending upwards in Iowa. Add in the fact that candidates that appeal to the evangelical vote typically win in Iowa--Huckabee in 2008; Santorum in 2012. This ought to be enough to suppose that Cruz would win. But the real reason that Cruz will win in Iowa is because of Iowa's caucus system. Iowa does not have regular citizens vote at the ballot box, as is typical of elections, rather Iowa has neighborhood meetings, or caucuses, in 1,682 locations throughout Iowa's 99 counties. At these meetings, or caucuses, the citizens will vote for Republican candidates and (for the first time) the results will be proportional and will be binding. According to the distribution of the votes at each caucus the groups will select delegates that promise to go to the county convention and vote the results of the caucus. So the battle for Iowa will boil down to whichever candidate has the best ground game and can mobilize supporters to attend the caucuses. Caucuses are (mostly) boring political party business meetings including local, county, and state issues culminating hours later in the selection of the presidential candidates. They keep the presidential voting to the last item on the agenda so people have to stay for the whole meeting. Consider your typical Trump voter vs. the typical Cruz voter. Who is more passionate about politics? Who is ardently pro-life? Who is more educated? Which candidate attracts people that have been engaged in the political process? Not Trump's. Trump supporters are people that are fed up with the political rhetoric and process and want an outsider. Trump's support might be wide, but it isn't deep. But most importantly, who will sit through three hours of local party politics in order to vote for their candidate? Not Trump's. And that is why Cruz will win Iowa.