After months of being written off as an un-electable candidate, former Pennsylvania Senator Rick Santorum nearly won Tuesday night's Iowa caucuses, losing to Mitt Romney by just eight votes. The Santorum surge, as it has come to be known, is credited largely to the Catholic candidate's strong support from evangelical Christians. CNN exit polling found that 34 percent self-identified evangelicals caucused for Santorum Tuesday, 19 percent supported Ron Paul, and that both Romney and Newt Gingrich took 14 percent of their votes. Mark Silk, professor of religion at Trinity College and religion and politics blogger, looks at the impact of evangelical Christianity on Tuesday night's Iowa caucuses.