While Mitt Romney leads in delegates, he has not yet won more than 50% of the delegates from any state. He did win 50% in Nevada.
After April 1, all states will award delegates from their polls and caucuses on a winner-take-all basis. If the other candidates win enough states to keep Romney from winning more than half the delegates (1144), they will arrive at the Republican Convention with a chance for a “brokered” convention. There, the first roll call of the states would formalize the primary and caucus results. Even though candidates are pledged to vote for someone, the results could push someone over 1144 and the candidate would have been chosen in the first roll call. Assuming it does not, then roll calls by state will continue until someone gets 1144.
In the second and subsequent roll calls, the people are not restricted to vote for the current 4 candidates. Someone else could be drafted, assuming they would go along. For example, if Mitch Daniels would agree to run if drafted, I think he would immediately win the nomination. Of course, among Romney, Santorum, Gingrich and Paul, if they are all still candidates, they could talk among themselves, and make deals. One of them could emerge as the winner.
Note that the primary/caucus season can only fail to produce a winner if there are 3 or more candidates. If, for example, Gingrich and Paul drop out, Romney or Santorum would win before the convention.
I believe that many are not satisfied with the current set of candidates and would welcome a brokered convention and the chance to nominate someone else. However, no one might step forward to become a new candidate. It’s a forlorn hope for many. But, wouldn’t it be a hoot?