The chance of Rick Santorum and Newt Gingrich forcing a brokered convention has become quite small. At this point, it is starting to come down to math, so forgive me for a bit of tedious delegate allocation arithmetic. After Illinois, Romney is estimated to have 560 delegates in his column, putting him about halfway to the 1,144 delegates he needs to win the nomination outright. While it is still theoretically possible for Santorum to do well enough to deny him that number, Governor Romney has a few things working in his favor.
First, the remaining states on the whole are more favorable to Romney. New York and California have large numbers of delegates at stake and are both very likely to go for Romney.
Other good Romney states like Maryland, Connecticut, and New Jersey are also among the remaining contests. Second, Romney’s key states tend to allocate their delegates using a winner-take-all method allowing him to quickly rack up delegates, while Santorum’s tend to use proportional allocation (and Gingrich’s key states are nonexistent).
For example, California’s 172 delegates are allocated using winner-take-all while the large state most favorable to Santorum, Texas, uses a proportional allocation process. Other potentially favorable Santorum states using a proportional allocation method include North Carolina, Arkansas, and Kentucky.
Finally, Romney continues to be in a much stronger financial position than Santorum. On his way to victory in Illinois, Governor Romney outspent Santorum by a margin of 7 to 1. This advertising and organizational edge matters a great deal and will persist unless something dramatic changes.
Enough with the math. The simple answer is that if Rick Santorum can’t win in places like Michigan, Ohio, and Illinois, he’s not going to be able to stop Mitt Romney from winning the nomination. Is there still a chance of Santorum forcing a brokered convention? Sure, but it’s small. The Wisconsin primary is on April 3. If Santorum can’t win there, I would move the odds of a brokered convention from small but possible to purely theoretical and realistically impossible.