Trump could do worse than name Ted Cruz, but Texas is going to vote to elect Trump in the general election regardless who he names as a running mate. Cruz knows how congress works, but would he be helpful to Trump in getting legislation passed? Would naming Cruz help him expand his base among Independents? Certainly not a slam dunk. Then, of course, we have the smear campaign Trump heaped on Cruz, including bringing his wife into it. Point is - would Cruz accept the VP spot? Who knows? I doubt it very much.
That said, Trump certainly should not consider Christie or Palin. Neither of these two people would add anything to the ticket - IMHO.
As a purely strategic move - adding electoral votes - Kasich will no doubt get strong consideration from Trump. He would deliver a badly needed state to Trump - Ohio. However, Trump can ill-afford losing the votes of even more conservatives than will likely already be the case in this election. Would Kasich reduce the unease many feel about Trump? Maybe.
I think a question that deserves raising is just how much or how little does the second person on the ticket make. My view is that the VP selection generally does not help very much - however, it CAN hurt. This is why I think Palin or Christie would be a disaster.
A name I have heard recently - Scott Brown, former Rep Sen from Mass. Just who we don’t need - a New England Democrat masquerading as a Republican. The man is useless as teats on a boar hog. What worries me is he has been showing up routinely on news/talk shows.
Here is a man I would consider - Sen. Mike Lee of Utah. A bona fide conservative who has not pissed off everybody in the Senate.
In the end, I think it will come down to Gingrich or Kasich. Of the two, I prefer Gingrich on a personal level, but does he give you additional electoral votes? I have no idea.