You can correct me if I am wrong, but the delegates that go to the convention are pledged supporters of the candidate who won in the state.
If that is correct, then the delegates of Rick and Newt would outnumber the delegates of Romney, and they would not vote for Romney. I understand it is the delegates who do the voting. (Is that correct?)
If their combined numbers do not outnumber Romney, then Romney already has a majority unless he is 30 or 40 short due to Ron Paul’s hundred or so by the end of the primary season.
I don’t think Paul delegates would support Romney either.
If I recall the rules correctly, delegates who are pledged to one candidate must vote for that candidate on the first ballot. On the second ballot the candidate can direct their delegates to cast their vote for the candidate of the candidates choice. IOW Gingrich could direct his delegates to vote for Santorum and vice-versa. I believe on the third ballot all delegates are released from the pledges and can vote for the candidate of their own choice.
I do know that at some point the delegates are all freed from their candidates and in such a case as that, Romney would be favored only because he is connected to the GOP-E and he also has the money to buy the delegates who are not all that committed to defeating him.
So if the convention is brokered, then Romney will most likely walk away from the convention with the nomination.
It is my understanding that Ron Paul people are surreptitiously signing up to be delegates for the other candidates. If they succeed in getting enough Ron Paul supporters in the ranks of the other candidates, Ron Paul could win this thing on the third ballot.
So, IMHO, a brokered convention is not a good idea. I don't think either Gingich or Santorum will walk away from a brokered convention with anything other than a VP slot. It's going to be Romney, or Christie or Jeb Bush or some other establishment GOP sell out.