Posters to this thread are correct: a broker or contested convention means one thing: an establishment republican will win. And most likely it will be Mitt Romney. At that point I throw up and go on a fishing trip the first week in November and pray the people who are prepping for the end of the world on December 21, 2012 are right.
If it goes to the convention I foresee total gridlock, and thus I think it's more likely Newt and Santorum would throw support behind an entirely new ticket (i.e. one without either of them on it) that represents their constituency reasonably well. I suspect the strategy would be a geographic play to lock up two of three between VA/NC, WI/MI/OH or CO/NM/NV. Given that my guess is McDonnell / Daniels.
Romney will just steer us towards fiscal disaster albeit a little slower than Obama.