As of this writing, only 3 U.S. Republican Senators -- Mike Lee, Lindsey Graham, and John Risch -- have endorsed Senator Ted Cruz for their party's nomination. What makes this so mystifying, is the fact that only Cruz can stop Trump from getting the 1,237 delegates needed to win going into the GOP Convention. So, one would think that most of the GOP Senators would be tripping all over themselves to see that he has significant wins in the remaining state contests.
But, no. The lack of Senators endorsing him merely re-enforces the notion that Cruz is disliked by the very people that had to work with him in his last 3+ years in the Senate. So much so, that they are willing to let Trump get his 1,237 delegates and, in doing so, avoid either a brokered or contested convention that could result in someone other than Trump being nominated..
In my opinion, this shows how unqualified Cruz is. Evidently, he's unable to work with his Republican peers; let alone with any Democrats. Do we really want a Presidential candidate that can't get anything done because of his personality? It must have really taken some effort on his part to literally become the most disliked man in Congress.
Endorsements for the Republican Party presidential primaries, 2016: https://en.wikipedia.org/wiki/Endorsements_for_the_Republican_Party_presidential_primaries,_2016#Ted_Cruz
Why Everyone (in Congress) Hates Ted Cruz -- NYMag: http://nymag.com/daily/intelligencer/2015/12/why-everyone-in-congress-hates-ted-cruz.html
Why D.C. Hates Ted Cruz - The Atlantic: http://www.theatlantic.com/politics/archive/2016/01/why-dc-hates-ted-cruz/426915/