On Friday in an interview on MSNBC's "Andrea Mitchell Reports," Arizona Sen. John McCain blasted his colleague Ted Cruz over the Texas senator's critique of the party's last three losing presidential nominees.

Here's McCain:

He can say what he wants to about me; he can say anything he wants to about  Mitt.... Mitt can take it. But when he throws Bob Dole in there, I wonder if he thinks that Bob Dole stood for principle on a hilltop in Italy when he was so gravely wounded and left part of his body there fighting for our country. Bob Dole is such a man of honor and principle and integrity. I hope Ted Cruz will apologize to Bob Dole because that's crossed a line that to me leaves the realm of politics and discourse we should have in America.

McCain's comments came 24 hours after Cruz made the case in a speech at the Conservative Political Action Conference (CPAC) that a purer form of conservatism was necessary if the party wanted to win in 2016. "All of us remember President Dole and President McCain and President Romney — now look, those are good men, they’re decent men, but when you don’t stand and draw a clear distinction, when you don’t stand for principle, Democrats celebrate," Cruz said.

It's not the first time the two men have clashed. Almost a year ago to the day, McCain described Cruz and his ilk in the Senate as "wacko birds." Cruz proudly owned the attempted slam; McCain apologized (though whether he was actually sorry is a whole different question). Then last fall, McCain hit Cruz's attempted filibuster of President Obama's health-care law as a misreading of the history of the fight over the law.

Two senators of the same party not liking one another isn't a new thing. (Frank Lautenberg and Bob Torricelli, anyone?) But the ongoing battles between McCain and Cruz are fueled by more than just personal animus -- although that's definitely in there, too. It's indicative of the broader differences between the establishment and tea party wings of the party and a leading indicator of just how nasty the 2016 presidential primary could get on the Republican side.

McCain, the party's 2008 standard-bearer, may think of himself as a maverick in Washington, but the truth of the matter is that when compared to the likes of Cruz, the Arizona senator is very much an establishment figure. McCain is a big believer that there is a way things are done in the Senate (and in Washington more generally), and one of the big no-no's is to attack former leaders of the party (particularly when that leader is in his 90s.) To McCain, what Cruz keeps doing is breaking the unspoken rules of the Senate for his own political gain. (Politics and baseball are similar in this way; they are both governed by scads of unstated but understood rules.)

Cruz, to put it bluntly, doesn't care about McCain and his unstated rules. (A clear illustration of Cruz's lack of interest in going along to get along? His decision to force his colleagues to vote on a clean debt-ceiling increase last month.) Not only does Cruz not care about these unspoken rules, he thinks they -- and people like McCain -- are part of the problem with the Republican Party.  By hewing to a set of rules on how to act, Cruz would argue that his party has lost its way -- straying from the sort of first principles that can get the GOP back into the White House.

And it's important to remember that not getting along or even actively feuding with the powers-that-be within the Republican establishment is very good politics for Cruz. No one in Washington thinks Cruz is doing anything but prepping to run for president in two years, and the more he burnishes a reputation as the guy who refused to play nice in the D.C. sandbox, the more his image as a tea party darling will be strengthened. And, say what you will about a profile like that in a general election, but in a Republican presidential primary, it's potentially quite powerful.

In short: Expect more of McCain vs. Cruz.