Not if they refused to endorse McCain.
No not at all. It's not okay to suck half as bad.
It is if you make statements in your “non endorsement” such as “JD would make a fine Senator” or “Obviously, my views are more aligned with JDs” or “JD’s a great guy”.
The fact that a colleague does not endorse a sitting politicians speaks volumes. And it does not say the same thing as running ads and making appearances praising the “maverick” RINO.