Even Mr. Santorum acknowledges that it's nearly impossible for him to amass enough delegates on his own to get the nomination. He just hopes to be able to keep Mitt Romney from hitting that number – 1,144 – as well.
“If the other people stay in the race, it's going to be hard for anyone to get to that magic number," Mr. Santorum said on CBS's "This Morning" on Monday. "We believe we get to the convention, the convention will nominate a conservative. The convention will not nominate an establishment moderate from Massachusetts."
If he (along with Newt Gingrich and Ron Paul) can perform just well enough to keep Mitt Romney from sewing up the nomination, Santorum suggests, then the party establishment could vote to go with him.
How likely is that?
The short answer: not very.
Despite the fact that the media and political pundits have been salivating about the idea of a brokered convention for several months, it remains a highly unlikely scenario.
At this point, Mr. Romney has – barely – a majority of the nominees in play. According to the Associated Press count (which includes the preferences of superdelegates who can support whomever they choose), Romney currently has 521 delegates, Santorum has 253, Mr. Gingrich has 136, and Mr. Paul has 50. That puts Romney at about 54 percent of the current total.
Gingrich's momentum also seems to have stalled, and Santorum alone – especially given the relatively small portion of delegates he currently has – seems unlikely to be able to keep Romney from getting to the magic number.
While Santorum at one time seemed to have a chance at taking Illinois on Tuesday, that possibility now seems distant, as Romney has moved well ahead in polls there. And Romney would likely need to lose in Illinois and other key states for a brokered convention to become a reality.
"Say that Mr. Romney wins the 16th Congressional District, which includes some areas on the far outskirts of the Chicago metro area, but Mr. Romney holds the other four," Mr. Silver wrote. "That would make the delegate count for the night Romney 40, Santorum 14, and put Mr. Romney ahead by almost 300 delegates – 561 to 267 – in the national total.
"That isn’t a close race, nor is it one that it is likely to require a brokered convention to resolve. If that is the count after Illinois votes, Mr. Romney would require only 46 percent of the remaining delegates to clinch a majority (he was won about 55 percent so far), and only 39 percent to clinch a plurality."
Brokered conventions are predicted fairly often, but seldom come to pass.
The last one was in 1952, when Democrats chose Adlai Stevenson as their candidate on the third ballot. In 1976, the GOP nominating process did go all the way to the convention – President Ford had a lead going into the convention but hadn't yet secured the nomination – but Ford managed to get the support he needed to win the nomination on the first ballot.
The New York Times reported over the weekend that the GOP is girding for the possibility of a brokered convention this year. It quoted Robert Duncan, a former Republican national chairman who presides over the council that hears disputes over delegates, as saying that "It's more likely than anything since '76."
But Mr. Duncan also said he doesn't really believe that it will happen, because momentum "is going to certainly push Romney – or somebody else – to the forefront."
If Santorum pulls a major upset and wins Illinois on Tuesday, expect talk of a brokered convention to increase.
But otherwise, it's likely that Santorum and others who don't want Romney will keep talking about it, but that Romney will eventually reach 1,144 – even though it may take him until June to get there.