What do you expect from a politician who wants to be re-elected from MA? The TEA Party knows who their candidates really are. If he goes too far left, he’ll be challenged in the GOP primary the next time he runs.
By the way, Brown, Rubio is a real conservative and will do just fine with his TEA Party base.
Incidentally, Rubio does not claim to be a Tea Party representative nor especially beholden to the TP base. He is a conservative Republican, and conservatives existed long before the current Tea Party emerged.
Rubio is more concerned with pleasing La Raza than upholding the Constitution.