With Super Tuesday now behind us, we can take stock of exactly where the race for the Republican nomination for President currently stands:
Donald Trump – He is the strong frontrunner and may be unstoppable.
Ted Cruz – He is clearly in second place, with more wins than anyone not named Trump.
Marco Rubio – He won the Minnesota Caucuses, but faces a mortal threat from Trump in his home state of Florida on Mar. 15.
John Kasich – He is stubbornly staying in the race until Ohio on Mar. 15, but has no path to the nomination.
Ben Carson – He finally dropped out.
The question that is on the minds of Republican leaders and the national media is simple: Can Donald Trump still be stopped, and if so, how?
I can see only two ways to stop Trump – and they directly conflict with each other.
The simplest way to beat Trump is to unite the non-Trump vote (which may be 60 percent of the GOP electorate) behind one candidate. Right now, with Cruz clearly in second place in overall delegates by a large margin over Rubio, he has the strongest case to make. He’s been able to win a significant number of states, raised more money in February ($12 million) than in any previous month, has a national organization, and has enough pledged delegates to have a path to the nomination.
But Cruz cannot beat Trump with two other candidates (Rubio and Kasich) splitting up the non-Trump vote – and he knows it.
The only option is for both Marco Rubio and John Kasich to drop out and unite behind Cruz, perhaps with Rubio as his vice president and Kasich as his defense secretary.
The calendar is driving the urgency.
RNC rules require all contests before Mar. 15, to proportionally allocate delegates, which has kept Trump’s lead fairly modest in February and March.
Starting Mar. 15, when Ohio, Florida and Illinois vote, the states become winner-take-all. If Trump wins the few winner-take-all contests, he will quickly become inevitable.
Trump’s opponents must force Trump to raise the ceiling on his support to 50 percent, which he has not been able to do.
Trump can undoubtedly win in a four-way race with 35 -40 percent, as he has consistently done.
But is 35 percent Trump’s ceiling, or is it his floor?
We may find out soon enough.
In this scenario, Rubio faces an excruciating choice.
Either support his rival Cruz and foreclose his chance to be the nominee. Or stubbornly stay in through Florida and be blamed for a Trump general election disaster, all while likely losing his home state to Trump and hurting Rubio’s own electoral future.
According to MSNBC’s Steve Kornacki, no sitting elected official in either party running for President has lost their home state since 1992. Rubio does not want to make history in that way.
Rubio is holding a donor retreat Mar. 10, and if the polls show he is certain to lose Florida he could drop out and unite behind Cruz a few days before the primary.
The second scenario is for everyone to stay in until the end and deny Trump the majority of the delegates that he needs to be the nominee. That delegate number is 1,237, and if Trump does not have that amount on the first ballot, 75 percent of the delegates can support whomever they choose on the second ballot.  
This is the “brokered convention” scenario that reporters love to hype. It hasn’t happened in over 50 years. It would be an ugly process. But it could work.
The central problem is that it would be ideal to have two serious options to stop Trump, but option one forecloses option two and vice versa.
The choice comes down to Rubio.
So the question for Marco Rubio is this: Just how badly do you want to stop Trump?
Mackowiak is an Austin- and Washington-based Republican consultant and president of Potomac Strategy Group, LLC. He has been an adviser to two U.S. senators and a governor, and has advised federal and state political campaigns across the country