In a Republican race in which Donald Trump has won three of the four states contested so far, Trump's rivals have begun talking more about winning delegates than states. From their point of view, Trump's victories in New Hampshire, South Carolina and Nevada, which in the past would likely have put a candidate on the verge of being declared the presumptive nominee, don't really mean much because so few of the 1,237 delegates required to win the Republican nomination have been allotted.

It's only on March 15 and after, the thinking goes, when GOP contests become winner-take-all, that winning states becomes truly important.

Marco Rubio, who has yet to win a state, has become the most articulate proponent of this view. The pre-March 15 states award delegates proportionally, Rubio explained on ABC the morning after his loss in Nevada. "By the time you get to March 15, now you're in some big states like Ohio and Florida that award all their delegates at once," Rubio said. "That's where you have to start winning states."

By Rubio's reasoning, a candidate could lose Iowa, New Hampshire, South Carolina, Nevada, Texas, Georgia, Virginia, Tennessee, Alabama, Arkansas, Oklahoma, Colorado, Vermont, Minnesota, and Massachusetts through March 14 and still be ready to rack up big wins once March 15 dawns. At that point, the change in delegate counting will turn around a struggling campaign.

That's theoretically possible. The practical problem is, how does a campaign go from losing everything before March 14 to suddenly winning after March 15? Delegate apportionment doesn't matter unless that fundamental change occurs.

A few days ago, a Twitter follower of mine, @Mellecon, wrote, "Rubio thinks the delegate fairy will save him on 3/15." The phrase describes some of the thinking going on not only in the Rubio campaign but in other corners of the Republican Party working to defeat Trump.

A considerably better-known political analyst, former George W. Bush strategist Matthew Dowd, has observed that anti-Trump forces have comforted themselves with various "myths" during Trump's rise, all to reassure themselves that Trump's threat was not serious. "Summer flings, voters will get serious, ceilings, Trump won't win a primary, organization matters -- and other establishment political myths," Dowd tweeted on Wednesday.

I asked Dowd whether the delegate count has become the latest such myth. "Yes, the delegate math rationale is now taking on the feel of all the other delusions the establishment has used to convince themselves," Dowd responded in an email exchange. "It is possible, but only matters if Trump momentum stalls or is stopped. And that won't happen unless he makes a major error that matters. Or someone else starts winning."

Was Trump's performance at Thursday night's debate in Houston a major error that matters? Did Rubio's aggressive takedown of Trump on healthcare amount to someone starting winning? It's hard for pundits to anticipate what voters will think after the debate has had a few days to sink in. It won't really be known until Super Tuesday. But whatever the fallout from the debate, the fact is, something big has to change for Rubio in just a few days.

Beyond claiming debate victory, the Rubio team points to several reasons why they believe the delegate situation will turn itself around. First, they note that late deciders in all the races so far have picked Rubio. Second, they believe that Rubio has gotten the support of many former Jeb Bush voters and will reap more if other candidates withdraw in the future. And third, they believe there is a huge opportunity for things to change — more debates, more voting, more dollars spent — between now and March 15.

Maybe that will happen. But to win enough delegates to prevail, a candidate has to win states. "If nobody has been able to beat [Trump] by the time the winner-take-all contests start on March 15, why would we think somebody would be able to start beating him then?" asks one strategist in the Trump circle. The answer is not clear, but that's what has to happen for Rubio to win.