Depends on the rules of the individual state primary.
Sometimes, they can be released. But, most commonly, they are committed to the candidate for one ballot. Sometimes, two ballots.
Someone said on here a few weeks ago that the nominee needs to win 5 states to get on the first ballot and if they don’t, their delegates are released to vote for whoever is on the ballot.
Perhaps now Newt will win those 5 states necessary to be on the first ballot. Maybe there will be a chance to play the steal-the-delegate game at that point.