The trouble, as I've written before, lies in the delegate math. Take Texas, where he finished in third place with 18 percent of the vote. In a truly proportional system, that would entitle him to around 26 delegates—more than he picked up over the four previous primaries combined.

Instead, he got three.

Some of the blame for that goes to Texas's statewide cutoff, which requires a candidate to receive 20 percent or more of the vote before they can grab any of the state's 47 at-large delegates. That's damaging enough, and relatively widespread among Super Tuesday states, but you can see the logic. It forces candidates to demonstrate that they can appeal to a substantial chunk of the state’s overall electorate.

The same rules apply to the other two-thirds of the delegates, who are awarded based on the tallies in each congressional district. In Texas, candidates can claim a maximum of three delegates per district, for a total of 108.

But here's the wrinkle: Even if candidates get more than 20 percent in a particular district, Texas only awards delegates to the top two candidates. If they’re in third place, they get nothing.

That's exactly what happened to Rubio. In six districts, he passed the 20 percent threshold but still trailed second-place Trump, often by less than 2 percent. Accordingly, he got nothing. In the end, he won his three delegates from three different districts, each time narrowly beating Trump for that coveted second slot.

All this can seem like small potatoes. But 502,000 people voted for Marco Rubio in Texas. Only 54,000 of them lived in districts where he won a delegate. The other 89 percent of his supporters? Their votes were useless.

And if that doesn't scare you, consider that Alabama and Georgia had nearly identical rules. Oklahoma and Tennessee had different cutoffs, but essentially the same system.

Only Virginia employed a truly proportional system of allocation. And it’s not coincidence that it’s where Rubio claimed his largest share of delegates on Tuesday night.