There reaches a time in every campaign in which the only people who are convinced that the candidate has a legitimate chance to win is the candidate himself and the most loyal (or ambitious) aides. The polls look rotten. Every argument against other candidates has been tried and lost. It’s time to pack it in — especially if continued participation in the race involves a dangerous outcome to the party and the country — but no one, not even those with his interests at heart, has the nerve to tell the candidate. Here is what someone should be telling Sen. Marco Rubio (R-Fla.):

With each round of voting, with the exception of Puerto Rico, your vote total has gone down. Your percentage is now down to single digits in some states, ones in which you were previously competitive (e.g. Michigan). You are trailing by double digits in your home state — before the poor showing on Tuesday. Florida insiders friendly to your cause do not think you can win.
You see big crowds, I know, and you think you are gaining traction. But you have said that again and again, only to come in third or fourth in multiple states. The percentage of people you see at rallies in Florida is minuscule compared with the number (probably close to 2 million) who will vote.
Stay in and you risk losing your state, ending your career on a terrible note and getting blamed for taking just enough away in states such as Ohio and Illinois to give Donald Trump, a man you have all but said is unfit for office, the nomination. 
Right now — until March 15 — you have remarkable leverage. You can endorse Sen. Ted Cruz (R-Tex.), asking that your roughly 150 delegates (more than enough to put him in the lead) vote for him, and likely get the vice presidential spot. Such a move would be an act of true statesmanship, forever banishing the image of a callow young man. It would dominate the news for days. Cruz would be seen in a whole new light — someone who can unite the party and who understands that politics involves winning people over. Your supporters and staff would see their efforts have not been wasted; you would be on a presidential ticket. (Once March 15 comes and goes, you’ve likely lost leverage to snag VP after losing more states.) 
Please don’t do the “I don’t want to be VP” routine. Of course you do, if it means in four or eight years you’d be next in line for the GOP nomination. Besides, like Vice President Biden, you could get plenty to do and be, as he is, “the last one in the room” on big decisions.
You say, why doesn’t Ohio Gov. John Kasich get out? He should, but if he does get out first and makes a deal with Cruz, you’d get no VP slot and would still come up short on March 15. Moreover, sorry to be blunt, but Kasich has a better chance of winning his state than you have of winning yours. (You are back in double digits, while Kasich trails Trump by single digits.)
And one last thing: Understand that if Trump gets the nomination, the party shatters and Hillary Clinton gets the White House, the Senate flips to Democratic control and Clinton picks the late Antonin Scalia’s successor.

That’s the spiel. Rubio should take it to heart and move promptly. Carly Fiorina’s endorsement of Cruz may be a sign that more support is on the way. What if Florida Gov. Rick Scott changes his mind and endorses Cruz? What if Mitt Romney or Jeb Bush do? Those endorsements would likely be enough to push Rubio’s chances to zero in Florida; if he exited after that, he would not have much leverage to make it onto the ticket and would be seen as leaving under duress.

We say this with no joy, having credited Rubio with courage on immigration reform and creativity in advancing a credible domestic agenda. He is by far the most electable of the remaining candidates, but to get to the general election one must win the primary. Blame the times in which we live. Blame the media obsession with Trump. Blame the voters who avert their eyes from ominous signs that Trump is a danger to the republic. Still, the choice for Rubio remains what to do now. The answer to many, many Republicans seems obvious.