It's basically impossible for Rick Santorum or Newt Gingrich to win a majority of delegates in the primary process. It is very unlikely that either of them could catch Mitt Romney in delegates. So the last hope is to block Romney from taking a majority of delegates into the convention -- that is, to keep him under 1,144. Is this doable?

Here's one way to look at it that works regardless of whether or not Gingrich drops out soon.

So far, according to the NYTimes Delegate Tracker, the non-Romneys have won about 431 of delegates to Romney's 495. In order to be more realistic, let's take a couple of states off the table: 37 Utah delegates go to the winner of the state as do 17 D.C. delegates. Utah being Utah, and Santorum missing the ballot in DC, it makes sense to give Romney those 54 delegates.

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So:

That means that in order to stop an outright Romney win, Gingrich, Paul, and Santorum need to pull in 713 of the 1,308 delegates that remain after today (and after Utah and D.C.). That is, they need 55% of the remaining delegates in order to block Romney.

Fifty-five percent may not sound like a ton, especially among three candidates, but compared to past performance, it is. So far, as the chart above shows, Non-Romneys have brought in 44%. To go from 44% to 55% of delegates involves increasing your delegate performance by more than 17% (44% X 1.17 = 55%).

Let me put it this way: take the upcoming Louisiana, Maryland, and Wisconsin primaries. They allocate 93 delegates through their primaries. Judging by past performance, the non-Romneys should combine for 41 of those 93 delegates. In order to get on pace to block Romney, though, the non-Romneys need to get 52 of those delegates.

What factors are so different, going forward compared to looking backward, that we would expect such a dropoff by Romney and a pickup by his opponents?