Clinton
1) Cruz
2) Fiorina (has been attacking Clinton effectively)
3) Rubio (also focused on Clinton)
4) Huckabee
5) Walker
(Trump is too friendly with the Clintons)
Sanders (socialist)
1) Paul (the perfect anti-Sanders)
2) Trump (capitalist vs socialist - no contest)
3) Cruz
4) Walker
5) Fiorina (another capitalist)
O'Malley
1) Cruz
2) Paul
3) Trump
4) Huckabee
5) Walker
Biden
1) Anything on two legs
2) Anything on legs
3) Anything with a pulse
4) Any organic matter
5) Anything with carbon in it
Terrific!
But in all seriousness, I think Uncle Joe shouldn't be underestimated. He would have 200% support from the Obama machine, which makes for a big GOTV effort among the blacks, Hispanics, Asians and MTV addicted youths.
Then it goes almost without saying that Biden will have the unions in his corner, blue collar as well as public employees. In fact, he has always done well with blue-collar whites, at least outside the South.
Last but not least, the MSM and other members of the chattering classes will be working overtime to boost his chances.
How would he do against various GOP opponents? Just too early to say. Maybe he'd lose against almost anybody. But still, I gotta think the contest wouldn't be beanbag.