I think your assessment of Hillary is myopic. She's more electable in a general election than anyone else on either side. There's very little hatred for her on the GOP side anymore--only from its radical fringe. Most of the Hillary Hate is coming from the left nowadays. But in the middle, which usually elects the president, she's seen as the adult in the room.
I wish Portman were more electrifying. I'm afraid Rand Paul is aiming for those dissatisfied 20s and 30s voters, and bizarrely, he seems to have a kind of charisma that the "kids" respond to.
The establishment of the GOP doesn't trust him, but they absolutely loathe Ted Cruz. If they see Rand Paul bringing in Obama's youth vote, they'll flock to him in an instant.
A Rand Paul vs. Hillary election would be a nail-biter.
A Rand Paul vs. Elizabeth Warren election would be fascinating. But it would mean that both parties moved during primary season: the Democrats to the left and the GOP to the libertarians.