UPDATE: By a very slim margin, GOP Presidential Candidate Mitt Romney has won the Iowa Caucus, narrowly beating his competitor Rick Santorum for the top prize.

LISTEN to Iowa Republican Party Chairman Matt Strawn announcing the winner HERE:

FOX News Radio's Jeff Monosso has more from Des Moines, Iowa:

Mitt Romney and Rick Santorum are walking away from Iowa with nearly an equal share of the votes, finishing in a virtual tie for first in the Iowa caucuses.  Both candidates managed more than 29,000 votes, more than 4,000 votes better than 3rd-place finisher Ron Paul.

Late into the night, the divide between the two candidates - who appeal to vastly different groups of voters - was minimal: less than one-hundred votes, just one-tenth of one percentage point.

Ron Paul and Newt Gingrich vowed to continue on with their campaigns, though Rick Perry - who finished 5th - is returning to Texas, where he will reassess his plans.