I read this piece today in the Times
http://www.nytimes.com/...
I think it has some merit. I personally am not "scared" of Hillary facing Rubio in the general, but I do think that he would far and away be the Republicans strongest candidate. That does not mean that I find him impressive in any way - I do not. But I do believe that he could put a dent in the Hispanic advantage that the Democratic part has, and I also think that he could win Florida.
Yes, I know, I know - his immigration stance will probably hurt him with both the Hispanic voting block and the RWNJ voting block - but I do believe that Democrats - and the Clinton campaign - should take Rubio very seriously.
The good news - from my point of view - is that I do not think he can win the nomination. However, I DO believe that he WOULD accept the VP slot, since he will be unemployed. And a Walker/Rubio ticket is definitely something to take very, very seriously.