Rick Santorum won North Dakota's Republican presidential caucus Tuesday.

Santorum was declared the winner shortly after 10 p.m. EST, when 40 percent of votes had been tallied. With 100 percent of results in, the results were: Santorum with 39.7 percent (4,510 votes), followed by Ron Paul in second with 27 percent. Mitt Romney, who many had expected to win the state, came in third with 25 percent.

It must have been a triumph of message, said Mark Jendrysik, chairman of North Dakota University's department of political science. People in North Dakota must have been waiting for [Santorum's] uncompromising social conservatism. It struck a chord with voters.

Jendrysik had said earlier Tuesday that he expected Mitt Romney to carry the state, based on North Dakota's tendency to vote for moderate candidates.

It's just unpredictable by nature, he said of the state. Its astounding.

Winning North Dakota's caucus added to Santorum's victories in Tennessee and Oklahoma on Tuesday.

Unlike most of the other Super Tuesday contests around the country, North Dakota's caucus is a beauty contest -- it's a nonbinding vote and none of the 28 delegates is guaranteed to be awarded based on the results.

The delegates will be assigned when North Dakota has its statewide Republican convention on March 30.

The convention usually follows the caucus, but it does not have to, Jendrysik explained.