That said, how long would it be before “Senator Rubio” became a mainstay of the centrists and considered it “his” senate seat, just like most the other “Republicans” now serving in the Senate?

Not that having a social and conservative vote for a term, maybe even two, wouldn’t be better than not having a conservative vote at all. But judging upon history of conservative Republicans changing into what can best be described as “RINOs”, unless Mr. Rubio is a man of honor greater than most of his future colleagues, I wouldn’t hope for more than a partial first term.