As the Republican primary season wears on, there’s a lot of discussion of delegate math. Jed Lewison of Daily Kos keeps making arguments based on raw percentages — Romney now has to win 48.4% of the remaining delegates available to reach the convention with the nomination in hand. I think he’s just doing propaganda, though, because he’s making the implicit assumption that delegate apportions are simple. So I took the delegate count from Real Clear Politics and made a super-stupid, basic spreadsheet.

I assumed that Romney, Santorum, and Gingrich would split the remaining primaries and caucuses with 30% of the vote each; I gave Ron Paul 10% of each state. Pause for outrage, yes, I know. If you split delegates, 30/30/30/10, Romney doesn’t get over the hump. But then I went back and gave Romney all of the delegates from the winner take all states: Puerto Rico, Wisconsin, Maryland, Washington DC, Delaware, California, New Jersey, and Utah. Utah should be pretty easy for him. Most of the other states ought to be easy Romney victories. Wisconsin is coming up soon; at 42 delegates, it’s a big prize and Santorum’s leading by a big margin there. Romney needs to take all the winner take all states to get to the delegate threshold. On the other hand, if he just misses Wisconsin, I bet there are enough unpledged delegates out there to push him over the top. Without Wisconsin, he’d be at 1152 delegates — with it, he’d be at 1110.

So OK, that’s kind of a rough road. Then I redid the numbers, assuming Gingrich drops and gets all his delegates to vote for Santorum. I gave 66% of Gingrich’s future support to Santorum, and 33% to Romney, which I think is a pretty reasonable estimate. In this model, Romney winds up with more delegates (1246) and he can afford to lose Wisconsin. Note that this scenario also works if you think Romney can pull in a mere 40% of the popular vote the rest of the way, even with both Gingrich and Santorum in the race.

Oh, wait, lemme fiddle with the model some more… OK. If Romney can get 34% of the delegates from proportionally allocated states the rest of the way, and win all the winner take all states except Wisconsin, he still winds up with enough delegates to win the nomination outright. He won 39% of the available delegates yesterday, so he made progress towards his goal. Romney’s right to think he can slowly push his way over the finish line. Lewison’s wrong; it wasn’t a setback. Also, Gingrich is not going to drop out because it would kill his ability to be any kind of a kingmaker at the convention.

Edit: this blog is a real professional doing the same kind of math, but much much better.