With Paul still in the race, it becomes much harder for whatever other non-Romney candidate might emerge, because the anti-Romney vote is suddenly split in two.

If Paul can continue to take 15 or 20 percent of the vote — or even just 10 percent — in these contests, the threshold of victory for Romney in that three-way race is much lower than it would be in a head-to-head race.

And the more Romney keeps finishing first, the more it will be clear that he’s the presumptive nominee, which will probably only increase the margin of his victories. At that point, it will likely be impossible for the non-Romney candidate to continue to fund and run a real campaign.