Donald Trump goes birther on Ted Cruz:

Donald Trump said in an interview that rival Ted Cruz’s Canadian birthplace was a “very precarious” issue that could make the senator from Texas vulnerable if he became the Republican presidential nominee.

“Republicans are going to have to ask themselves the question: ‘Do we want a candidate who could be tied up in court for two years?’ That’d be a big problem,” Trump said when asked about the topic. “It’d be a very precarious one for Republicans because he’d be running and the courts may take a long time to make a decision. You don’t want to be running and have that kind of thing over your head.”

Of all people, Donald Trump is the last person to use a metaphor of something hanging over his head.

Meanwhile, Chris Christie calls Marco Rubio “slime.”

Signaling a turn among center-right candidates into a tougher phase, Sen. Marco Rubio charged that Christie has been too closely aligned with President Obama on gun control, health care and Common Core education standards, echoing twin attack ads aired here by his allied super PAC. Meanwhile, allies of Ohio Gov. John Kasich filled mailboxes in New Hampshire with a biting pamphlet that reads, “Chris Christie: Tough talk. Weak record.”

In an interview Tuesday with The Washington Post, Christie responded with a sharp broadside against Rubio and shrugged off Kasich, vowing that voters would coalesce around his candidacy in spite of his ideological impurity because he projects strength.

“I just don’t think Marco Rubio’s going to be able to slime his way to the White House,” Christie said. “He wants to put out a whole bunch of negative ads? Go ahead. I hope that he will acknowledge at some point that I couldn’t care less.”

To be sure, this is how primaries usually go: vicious and bloody until the great moment of unity where they all sing together and go after the other party.  But this one has been especially brutal with the added unpredictability of Donald Trump’s campaign that has more resembled a schoolyard shouting match than a discussion about policy.  (By the way, Rachel Maddow is comparing the Trump campaign to the George Wallace campaign of 1968.  Been there, done that.)

The betting is that either Mr. Cruz or Mr. Rubio are going to be the eventual nominee next summer after a nasty convention, leaving the Democrats to save a lot of money on campaign ads by just posting links to YouTube.