Although I have no evidence to back it up, I believe that Cruz only ran for the U.S Senate as a platform to run for President, and isn't interested in being a senator for the long haul.
Oh, you mean just like Hillary Clinton who only ran for the U.S. Senate from New York in 2000 as a platform to run for President, and wasn't interested in being a Senator for the long haul.
At least Hillary was able to finish a term, and didn't spend her entire tenure in office grandstanding and attention whoring.
At least you don't deny that Hillary only ran for U.S. Senate in order to have a political base from which to run for the Democratic nomination for President.
And I am sure Cruz will finish this Senate term, unless of course he is elected President. And if he is not elected President, he will run for re-election to the U.S. Senate in 2018.