[cotton1706]

“Since Mike Lee and Ted Cruz are prohibited from endorsing an opponent of LG”

I don’t think they’re prohibited. It just looks to be in bad form to endorse an opponent of a colleague, especially of one’s own party. But it’s been done. Bill Frist endorsed John Thune and Jim DeMint endorsed Pat Toomey (which caused Specter to change parties).

[Servant of the Cross]

At a closed-door lunch meeting of Senate Republicans Wednesday, the freshman conservative told his colleagues that he would not intervene in their 2014 primary fights or fundraise for the controversial outside group. Cruz added that the SCF’s decision to try to defeat sitting GOP senators in their primaries was its alone, according to several people familiar with the session.

This was in response to Mitch McC's ambush of him at a closed-door Senate lunch.