PURCELLVILLE, Va. — With Super Tuesday hours away and make-or-break contests coming up March 15, we have entered the most intense and emotional two-week period of the Republican presidential campaign so far. Crowds are bigger, applause is louder, feelings run deeper.

Just consider the events of the last few days. A wild debate in Houston. The emergence of Marco Rubio, the insult comic candidate. The Christie endorsement. And then, on Sunday, Trump's refusal to disavow either David Duke or the Ku Klux Klan, setting off what could become an epic wave of rancor inside the GOP.

It was all very … intense. And at Rubio's well-attended rally here at the conservative Patrick Henry College Sunday afternoon, there were hints the campaign can be too overwhelming for some well-meaning voters trying to make a decision.

Scott and Stephanie Sloan, of Purcellville, told me they came to the rally undecided, but decided after hearing Rubio that they would vote for him. I asked who were the candidates they were considering when they arrived, and they said Trump and Rubio.

When we talked, they hadn't heard about Trump's Duke-KKK exchange on the morning shows; they had been in church. But even so, Trump had become too much for them.

"I think it's just the circus that surrounds Trump is just a little bit over the top," Scott told me.

"He's a little too much crass, and not enough class, I guess," added Stephanie. "He's just a bit of a loose cannon."

I asked what they liked about Trump to begin with. "I think a lot of people are intrigued by him because he's not a part of the establishment," Stephanie said. "He's an outsider, and he's like, hey, I can do everything differently."

But the Trump circus was too much; he faded from consideration. Then the Sloans saw that Rubio would be appearing nearby on Sunday. They liked what they heard. "He reminds me of my parents and my parents' parents," Stephanie told me. "Someone who came from parents who had to work for everything they had. That resonates with me."

So here's the theory, not just from Scott and Stephanie but also from talks with voters in Iowa, New Hampshire, and South Carolina who were receptive to Trump but couldn't quite commit:

Everyone has a certain tolerance level for uncertainty, disorder, and controversy. If a candidate's campaign stays below that level, all is fine. If it climbs above that level, a voter may begin to think a candidate is more trouble than he's worth. The voter sees the campaign as an taxing experience -- it's just one thing after another -- and looks for an alternative choice.

The problem is, Trump has an apparently infinite tolerance for uncertainty, disorder, and controversy. He can be comfortable and prosper in a campaign that just wears some of his voters out. By Sunday, the Sloans had hit that point — and that was before they heard what Trump said on the morning shows.

Other Rubio supporters in Purcellville were in a strongly #NeverTrump mood. "I cannot vote for Donald Trump," Sara Brady, of Vienna, said. "I may have to vote for Hillary, if Rubio doesn't get the nomination. Donald Trump is a lunatic." Brady was dismayed at the "bathroom humor" Rubio has adopted against Trump, but said Rubio was forced to do it. "If you're attacked, you have to fight back."

"He's a disaster," said Cheryl Buford, of Vienna. "He's a con man. I think Marco nailed it."

"I could live with Cruz, quite frankly, but Rubio is the only candidate who inspires us," said Bill Cullo, of Alexandria, there with wife Tracy. Both have worked in politics in the past.

Trump? "She sees Trump as the End of Days," said Bill, nodding toward his wife.

"Oh, my God," said Tracy.

Over the course of the campaign, Trump has been compared to any number of dictators and strongmen. Carlos Chaves, of Dumfries, said he saw something familiar in Trump. "I lived in Venezuela for two years," Chaves told me. "The way [Trump] speaks and the way he expresses himself are very similar to how Hugo Chavez expressed himself to the people. So I don't want to make the mistake of electing someone who is like that."

There haven't been a lot of polls in Virginia. Only one, from CBS-YouGov, measured voter sentiment after last Thursday's debate. (It found Trump up by 13 points.) Before that, Monmouth had Trump up by 14. The Purcellville rally was in Northern Virginia, an hour outside Washington. It isn't Trump country, and there was a lot of enthusiasm for Rubio in the room. But the question is whether enough Virginians will come down with Trump Fatigue to prove the polls wrong.