The Republican party had a brokered convention in 1952 and nearly had one in 1976. It may be unlikely but it is possible.
Actually this is a year when a brokered convention is a real possibility. It all depends on how many delegates Ron Paul collects and how close the Gingrich-Romney race becomes.
If Romney and Newt end up with, for example, 48% and 49% of the delegates and Ron Paul has the remaining 3% then he could swing the vote one way or the other. I know it's a scary thought but there is at least a possibility that Ron Paul will get to pick our nominee for us.
If there is a brokered Republican convention in 2012, I will eat my hat.