"It was fine to come in third in Iowa's caucuses, when he saw a late surge and was running against 11 other people. It is not fine to come in third in Idaho in a field of four candidates. It is not fine to win 16 percent of the vote there, when you need 20 percent in order to qualify for any delegates. It is not fine at all to come in fourth -- dead last in the current field -- in both Mississippi and Michigan, qualifying for delegates in neither.... So now Rubio's campaign is spending the day doing two things. One, it is brashly predicting that it will win Florida. Second, it is insisting that it will still exist by the time of that vote next Tuesday."
From "Marco Rubio’s campaign is basically over" by Philip Bump in WaPo.
I'm looking at the new Florida polls. It seems obvious to me that if Rubio is interested in stopping Trump, he should get out before Florida and allow as many of his votes as possible to go to Cruz. He should endorse Cruz now. It's the one thing he can do, and since it is so clear, if he fails to do it, he's responsible for Trump's getting the nomination. Now, maybe he thinks Trump is better than Cruz. If so, stay in. That's how I'm going to read it.