CBS News echa un vistazo al calendario y la matemática:
The case for Romney: With 645 delegates, according to CBS News estimates, Romney is now past the halfway mark to the magic number of 1144 to clinch the nomination. That still leaves a ways to go, but there are a lot of delegates still available - about 600 in April and May, either through direct primaries or in state conventions in states that have already held caucuses.
Romney has won 60 percent of the delegates to date, as estimated by CBS News, so if he keeps up this pace, it's possible for him to reach 1144 on June 5 when delegate-rich states of California (169 delegates at stake) and winner-take-all New Jersey (50 delegates) hold their contests. Romney would have to pick up the pace for him to clinch the nomination at the end of May, needing to win just over 80 percent of the delegates available between now and then. However, there are fewer competitive candidates now than in the early contests and with some more moderate electorates holding contests on April 24 it's not totally unreasonable to think Romney could meet that.
The case for Santorum: Santorum has claimed that he can stop Romney from reaching that magic number of 1144. For this to happen, Santorum would have to win about 60 percent of the outstanding delegates, though importantly, doing so would not give Santorum enough delegates to clinch the nomination himself. It would just stop Romney from doing so. By CBS News estimates, Santorum has won 24 percent of the delegates allocated so far; He would have to more than double his delegate-winning pace.
When we look at both the calendar and the allocation methods in the states, it seems to point to late May or early June as the earliest that Romney could clinch, if he does. Most of the remaining contests allocate their delegates using more proportional methods, making it more difficult for Romney (or any candidate) to deliver a knockout blow soon. But there are some states where Romney is likely to win significantly more delegates than his opponents. New York on April 24, where Romney leads big in recent polls, allocates its 58 district-level delegates winner-take-all. If a candidate wins a Congressional district (no matter the margin) then that candidate wins the district's two available delegates while the rest of the candidates would get zero in that district. Romney is likely to rack up a lot of delegates then. Connecticut, also on April 24, allocates its Congressional district delegates in a similar way.
In Santorum's home state of Pennsylvania, votes are cast directly on the ballot for congressional district delegates. These delegates are not officially tied to a presidential candidate and go to the national convention technically unbound, but a more organized campaign is likely to have an advantage in getting its supporters on the ballot as delegates. So a win in the statewide vote for Santorum in Pennsylvania doesn't necessarily mean a huge delegate lead for him in the state.
The month of May includes some Southern states that have been friendly territory for Santorum. He's likely to gain some delegates then but many states voting in May use proportional allocation, meaning even a second or third place finisher can win some delegates. The biggest delegate prize in May is Texas with 152 delegates at stake, but the state allocates all its delegates proportionally based on the statewide vote. Even a big win for Santorum here wouldn't give him all of the state's delegates. Under current rules, a candidate does not need to win a certain percentage of the vote to be awarded delegates.
Efforts are being made by some Santorum supporters in Texas to change its primary to a winner-take-all contest but such an outcome would require a waiver is unlikely.
Santorum backers see another possibility in the delegate allocation. Many of the states that held caucuses earlier in the primary season will be holding conventions in the coming months, which is often where the delegates are actually chosen. These delegates sometime reflect the results of the caucus results but sometimes they don't. This is where campaigns can work to make sure their delegates are chosen to go to the convention.
Many unpledged delegates (these are the Republican National Committee members who are free to support whomever they choose) have yet to commit their support for a candidate. There are 120 or so of these delegates and according to CBS News estimates, 34 are backing Romney, 5 are for Santorum, while 2 are for Gingrich. The rest are uncommitted at this point so their support is up for grabs.