Jim Newell, Slate:
The options for the GOP to find someone who can take Trump one-on-one are now a candidate with the most room to grow, but who hasn’t come close to winning a contest, and another candidate who’s won a contest but is having trouble expanding his support beyond very conservative voters.
On the whole, Rubio has the better argument. With Jeb Bush now officially out of the race and John Kasich living on fumes, he could suck up enough votes (and money) to turn in stronger performances than he has so far. And the calendar will get much more favorable to him—or, at least, much less favorable to Cruz—beginning on March 15.
But even if Cruz does begin trending behind Rubio, what rationale will there be for him to drop out? Most candidates drop out when the money’s gone, and money is not a problem for Cruz. If his support isn’t likely to grow much with Rubio still in the race, neither is it likely to collapse. He can stay around and hope to catch fire at some point along the way—or at least try to secure enough delegates to deny any candidate an outright majority, and take his claim to the convention.