The guy is interesting, but I wonder if he even has the ambition. For example, he is one of the democratic Senator that introduced the least bills in the last congress. He really doesn't try to be in the spotlight. He didn't even get a speech at the DNC.
Of course, that could also be an advantage. He could be the new young handsome Senator from a diverse, dynamic state, that nobody has ever heard of. This is how Jimmy Carter became President, after all. Also, he has been voted the most handsome Senator.
Definitely top three(Jeff Flake, Martin Heinrich, Mitch McConnell).