It's called a career-limiting decision. Couldn't have been a better endorsement of RP.
RP will likely not get the nomination, but it might be that he runs third party because of a swelling in support. He'd likely get BO re-elected. Then, you never know.
But first, the Republican convention. Like the Presidential election, the people do not elect the winner. It's the delegates who vote, not the people. The caucuses are another joke.