These are the two foreseeable matchups.
Bush vs Hillary (might as well stay home, both of them suck, vive la revolucion)
Paul vs Sanders.
Cruz (if deemed eligible) vs Warren.
The above three matchups are 50-50, there's no way of telling how they'd swing.
However, if we mix these candidates up:
Hillary > Cruz
Paul > Hillary
Cruz > Sanders
Sanders > Bush
Warren > Bush.
Paul vs Warren is also 50-50
Notice that neither Paul nor Warren would be curbstomped by the other candidates (of course this my opinion).
Bush > no one, but still 50-50 with Hillary.
So if Hillary is nominated, then we best nominate Paul.
This is based on my interactions with real people in my own community and non-MSM internet trends (except Bush vs Hillary, obviously only MSM sources endorse that one).
So, without knowing who the candidates will be, it appears that Democrats have a slight edge in taking the White House in 2016.
Rand Paul will not be the nominee.
Your list also discounts Walker, Kasich, and other strong candidates.
The Dems have no one. The party has eaten its moderates and the hardcore left is in charge. And thsoe people just proved theycant get elected.
Walker is an extremely risky matchup against Warren, he'll either win in a landslide, or lose in a landslide. Barely anyone knows who Kasich is, and Rand Paul has a lot of popularity and name recognition, without having to rely on his father's legacy anymore. Rand Paul is a superstar, because he is exactly who he appears to be, even if everyone disagrees on various different stances with him.
And don't underestimate the allure of inspirational socialists like Warren to the masses. Look at the minimum wage votes in red states during 2014. All Warren (politically) needs to do is call Obamacare a "corporate mess and insurance company hojacking of the health care system" (which it is), and say "I'm going to repeal Obamacare and implement Single Payer/National Health Insurance" and you have a very Power (and dangerous to America!) candidate.
I know you're mcuh older and more experienced than me, certainly you wouldn't be so folly as to write off the socialists, especially when they're now going to reveal themselves openly, like Lawrence O'Donnel? Certainly you've noticed the campaign being launched to disassociate socialism from communism?
AntiParty ever so cleverly made a thread on that today (because he's a Marxist political hack, masquerading as non-politically-affiliated member of USMB).
Think of Obamacare as the sacrificial head of the Hydra:
It was meant to be cut off, so the socialist "alternative" replacement could be ushered in. Obamacare is the "crisis" intentionally created by both Neocons and Progressives (Oromneycare) and Single Payer will be the "solution." Neocons are in fact socialists, ones that like to use government welfare to bail out big banks (which is fascism). They are National Socialists to be exact. There is no "left vs right" in America on the establishment level, it's Fascist Left vs Communist Left.
Ron Paul is the true small government "right."