Sen. Marco Rubio (R-Fla.) in Salem, Va., on Sunday. (Don Petersen/Roanoke Times via the Associated Press)

This weekend at least felt like a tipping point in the Donald Trump phenomenon. Partly the feeling is attributable to Sen. Marco Rubio’s demonstrated ability to draw huge crowds and substantial free media to his all-out battle against Trump. In taunting Trump, denouncing him for failure to condemn David Duke and the Ku Klux Klan and making his own campaign into a crusade to stop Trump from absconding with the GOP, the senator from Florida helped dispel the sense of fatalism gripping many Republicans and shred the mainstream-media narrative that the race is all but over. The media — which slavishly covered every Trump rally and afforded endless free media access — is now aghast that Rubio would make fun of Trump’s spray tan, tiny hands and business failures. Rubio, it seems, has hit a nerve and deprived liberal pundits of the certainty that Hillary Clinton will get to face in the general election a vulgar bigot.

Trump is now sputtering, backtracking and trying to defend his Trump University racket. Even Joe Scarborough, one of his most reliable apologists, has turned against him. (“It’s breathtaking. That is disqualifying right there. To say you don’t know about the Ku Klux Klan? You don’t know about David Duke. . . . I mean, is he really so stupid that he thinks Southerners aren’t offended by the Ku Klux Klan and David Duke? Is he really so ignorant of Southern voters that he thinks this is the way to their heart — to go neutral, to play Switzerland when you’re talking about the Klan?”)

During appearances on network television Feb. 28, Republican presidential candidate Donald Trump repeatedly declined to refuse the endorsement of David Duke, a former grand wizard of the Ku Klux Klan. While Marco Rubio and Ted Cruz both took aim at Trump. (The Washington Post)

Moreover, the floodgates have now opened and the Trump business failures and scandals are pouring out. The Post reports today:

In the spring of 2006, the tycoon hosted a glitzy event at Trump Tower to introduce Trump Mortgage LLC, a new firm that specialized in selling residential and commercial real estate loans. He devoted a floor of the Trump Organization headquarters at 40 Wall Street to the new business. And his picture appeared atop the company website with the instruction: “Talk to My Mortgage Professionals now!”

“I think it’s a great time to start a mortgage company,”  Trump told a CNBC interviewer in April 2006, adding that “the real estate market is going to be very strong for a long time to come.”

Within 18 months, as the experts’ worst fears began to pan out and home prices began to dip, Trump Mortgage closed, leaving some bills unpaid and a spotty sales record that fell short of Trump’s lofty predictions. Trump distanced himself from the firm’s demise, saying at the time that he had not been involved in the company’s management and that its executives had performed poorly.

He ignored repeated warnings about the housing bubble. And when the business failed — no surprise — “Trump blamed the people he hired to run the company.” Then he failed again: “After Trump Mortgage closed, Trump tried again to enter the world of mortgage lending, licensing his name to a firm once known as Meridian Mortgage, which would also be known as Trump Financial for a few years going forward. It was led by an experienced New York mortgage executive, David  Brecher. But, like its predecessor, Trump Financial quietly ceased operations.” Like his ventures into steaks, the United States Football League, airlines, casinos and other flops, Trump moved on while employees lost jobs.

If Trump’s image as a “winner” is shattered, will his fan base stick around? We will find out soon. If his image as the Midas-touch mogul is replaced with that of a privileged scion of a successful father who went from one glitzy business to another, never making good on his marketing, voters may come to suspect, just as Rubio claims, that he is a lucky con artist who cares not one whit about the little guy.

Political expectations and voting preferences do not change overnight, so Trump is still likely to do very, very well Tuesday. A funny thing happened in the expectations game, however. Trump is now expected to win everywhere and rack up an insurmountable delegate leadIf he does wind up losing in some states, his aura of invincibility may take a hit. And many pundits still do not appreciate how the campaign calendar and proportional delegate count buy Rubio and others some time.

After Super Tuesday, about 25 percent of the available delegates will have been awarded. After March 15, that number goes to about 50 percent. If the tide turns, Rubio has plenty of winner-take-all contests and delegate-rich states such as Florida (99), Illinois (69), Pennsylvania (71), California (172) and New Jersey (51). In short, even lead of a few hundred delegates after March 1 does not lock in the nomination for Trump.

But what about history? Momentum? The normal pattern is that the consensus candidate/eventual winner emerges early on and then continues to rack up wins. But there is no “normal” in 2016. The front-runner has a vibrant but limited base of support and, for now, extremely high negatives. The field has only just shrunk from 17 or so to five, and is likely to get down to 2 or 3 in the next couple of weeks. Like all bubbles, the Trump bubble can burst as quickly as it inflated.

In short, what Rubio — who after Super Tuesday may be the only candidate capable of stopping Trump — needs to do is prompt a huge change in momentum. Did he start that this weekend? Maybe. What we can say is that this is the sort of shift in tactics, style and energy that one would need to accomplish that needed about-face.