Ezra Klein offers a fantastic list of 21 reasons Newt Gingrich won't become the GOP nominee, ranging from his palling around with Democrats to his absurd defenses for his adulterous affairs to his confusion of sci-fi and reality. Please read it. But I'd assert that there's a bit of a leap from the final item on his list to the statement "And I don’t believe they will choose someone like that."
That is to say, Ezra shows us why Gingrich won't become the nominee, but not how he won't become the nominee. That's trickier. Remember, even though Gingrich is way behind in endorsements, he's currently polling way ahead of Romney et al. in the earlier primary and caucus states. So how do elite preferences get translated into votes?
The key thing here is that Gingrich has no backers. Romney can slip up -- make a silly statement or give a bad interview -- and there are legions of journalists and elected officials who can explain it away or provide context or still point to his other qualities as a candidate. When Gingrich messes up -- as he most assuredly will at some point in the next few weeks -- no one's got his back. He'll be on his own, forcing to either recant what he said (flip-flopper!) or double down (loony!). What will his next apostasy be? I don't know, but it's exciting to watch.