Maine Republican Party Chairman Charlie Webster made the announcement on Saturday. Romney has picked up 21 more delegates.
Paul was the only other GOP candidate campaigning in the state; Rick Santorum and Newt Gingrich did not actively participate in the race.
- Romney received 39 percent of the vote.
- Paul received 36 percent of the vote.
- Santorum came in third with 18 percent.
- Gingrich received 6 percent of the vote.
Romney had planned to take the day off, but did some last minute campaigning in the state. During a visit to Sanford, he told supporters that it will take a businessman and a Washington D.C. outsider like himself to get the country back on track.
Some Maine communities have yet to hold their caucuses, though party leaders say they don't plan to count those votes.
Romney easily won the Maine caucuses in 2008.
The Associated Press contributed to this story.