Just over four-in-10 Republican caucus participants say they were personally contacted by someone trying to get them to support a particular candidate. According to the NBC News Entrance Poll, these outreach efforts are more likely to be reported by veteran caucus-goers rather than first-time participants.
Caucus-goers age 50 and older are also more likely than those under 50 years old to report receiving a candidate contact. The big question is whether this ultimately made a difference in candidate support as the results start to come in.
Iowa Caucus: Complete coverage and live updates
Iowa is supposed to be all about organization. The conventional wisdom is that you can't win in Iowa without a good ground game. In the 2012 Republican contest, Rick Santorum rode a late surge in the polls to bring out stalwart evangelical voters who helped him squeak by with an upset win over Mitt Romney.
There has been some question about who has the best field operation this year. Ted Cruz is working many of the same constituencies that propelled Santorum to victory four years ago. Marco Rubio has also invested resources in getting out his vote. The extent of Donald Trump's efforts, though, are not as clear. Will his huge rally crowds translate to higher turnout than the old fashioned press-the-flesh diner tours taken by his competitors?
Read how NBC News projects elections results here.
Read the difference between an entrance poll and an exit poll here.