"He's a show horse, not a workhorse," Thurber said of Cruz. "And that had been a very strong norm for 50 years."
"The consequences for the Republican Party are very serious because they don't have a clear strategy and message that they cohere to. Basically, they have a civil war going on and part of that civil war is the balkanization of positions."
The fundraising model has changed, too, increasing the likelihood that other politicians can follow Cruz's lead. Anthony Corrado, a professor at Colby College in Waterville, Maine, and an authority on campaign finance, said it is possible now for candidates to have a financial constituency and to generate support for candidacies "without the traditional party structure."
"What we are seeing — and I think we saw the early roots of this in 2012 — now is the financial constituencies are starting to divide along more ideological lines within the partisan sphere," Corrado said.
"That will fuel intra-party divisions and factionalism," he said. "To the extent that party support served as a constraint on candidates, that constraint is becoming less effective. The rules now facilitate more unilateral behavior."
That explains why a group of Republican congressmen, with Cruz most prominent among them, "has decided that ideology and principle is what's most important and they don't care much about the operations of the Senate and government."
Cruz said he sees "a new paradigm in politics, the rise of the grassroots." As he campaigns for Republican candidates in 2014 and ponders his own future, he will be testing whether that new model holds.
"He is a star now burning through the atmosphere, and the issue is whether he is going to burn out returning to Earth," Corrado said.
— With assistance from Julie Hirschfeld Davis in Washington.