But have people heard of him? Name recognition is extremely important; hence my assumption that Romney and Biden are the most likely replacements. (Sanders may be likely to get the nomination if Hillary stumbles, but I’m afraid the “Socialist” would be the heavy underdog in November. 
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Hillary is the clear #1. Rubio is #2. I don’t think anyone else has a real shot right now.
Clinton, Trump, and Rubio.
Trump don’t deserve being mentioned in that company.
I know the OP says to vote for three, but I’m only voting for Clinton and Rubio, because Rubio’s the only one of the Republican candidates where I can currently see any reasonable probability of him both winning the party nomination and then defeating Clinton. As for the rest, there’s some I can see winning the nomination but definitely losing the general election (Trump, Cruz, Jeb!), a couple I could see potentially giving Clinton a serious run for her money but who have no chance to win the nomination (Kasich, maybe Pataki), and plenty with barely a snowball’s chance in hell of winning either one (most of those yet to be mentioned from the clown car).
In the spirit of the OP, I think the two most likely scenarios are Trump vs. Clinton and Trump vs. Sanders, so I picked Trump, Clinton, and Sanders.
Hillary will be the next president. This is coming from someone who vastly prefers Sanders.
There is not one Republican in the bunch who can beat Clinton, but of all the clowns in the car, I’d say Bush is the least clown-like (clown-ish? clowny?), so if I must play the game: Clinton, Sanders, Bush.
You’re right about one thing: the White House is Hillary’s to lose. But Sanders has no hope of being President. Rubio is, at present, the only person I can imagine in the white House besides Hillary.
It’s interesting to me that Sanders has more votes than Jeb Bush. Pleasing. I really have not liked that guy since the whole Terri Shiavo thing.
I went with Clinton/Rubio/Bush. Seems to be a standard combo for this question, but I just don’t see anyone else getting in. Hell, I can’t really see Rubio or Bush being nominated, but I think the Republicans have to nominate somebody…
Kamala Harris may have a great career ahead of her, but she’s running for the office she’s qualified for at this point (Barbara Boxer’s Senate seat) - no way does she jump to President. Has the Republican clown car really convinced people that the Presidency is some sort of low level position that any old real estate developer, surgeon, failed CEO, or state AG can run for successfully? It doesn’t work that way.
Didn’t read OP before voting so I only put it in one name. But given halfway decent odds, I would bet actual cash money on Cruz.
#2 and 3 would be Clinton and I guess Trump.
Dark horse: Biden
Cruz and Trump being the other possibilities
Rubio is undoubtedly the least respectable and whose election would carry the most negative implications regarding the American electorate of the individuals mentioned in the previous post.
Great thread-title/post combination!
I agree that Trump might well be a better President than either Cruz – with sociopathic political “ideals” – or the callow Rubio – who, like GWB, would just be playdough in the hands of his (Koch-chosen?) advisors.
The only way Biden becomes the next President is if Obama dies or is incapacitated in the next year. He literally cannot jump into the primary race any more, due to filing deadlines that have already passed, and with only two candidates running, there is no chance of the Democrats going into a brokered convention.
And while Trump has a reasonable chance to win the Republican nomination, he’d be destroyed in the general election versus anyone the Democrats field.
Clinton, duh. I think O’Malley has a better chance than Sanders, but both are near zero. On the GOP side I voted Rubio and Cruz but I thought pretty long (several seconds) about Trump. I’m surprised Trump has fewer votes than Bush. Trump still has an actual shot at winning the GOP nomination. Bush has basically no chance at the nomination.
This is clearly false. Obama could also resign or be impeached and convicted. 
As someone who voted Bush and not Trump (in this poll, that is), I disagree. Bush is unlikely to be nominated, but he does have a path. And that path is to quickly figure out how to run a campaign, hope Cruz delivers a knockout (or at least TKO) to Rubio, and position himself as the champion of the establishment lane. If previous years’ trends are to be believed, the vast majority of Republican primary voters are actually still undecided, and after they finish throwing their quadrennial fit, they tend to go with the establishment guy.
As for Trump, while I can see why one would think he has a better chance than Bush of winning the nomination, it doesn’t matter. He can’t win the general. So his chance of becoming President is zero. Bush’s remote chance of winning the nomination gives him a > 0 chance of winning of the Presidency, so he’s a better bet in this poll than Trump.
But California was already a blue Democratic state. It’s no added advantage.
Or if Hillary becomes incapacitated. IANAL, but I think the Democratic convention can end up doing what it wants, and what it will want (if Hillary is unable) is Biden – the candidate most likely to win.
It’s a longshot (and I’m not wishing ill on anyone), but people in their late 60’s do sometimes get health problems. I’d have clicked on Biden if OP asked us to click FOUR names instead of three. (Cruz may have an excellent chance of winning the GOP nomination but – maybe it’s wishful thinking – even the American people couldn’t be stupid enough to elect him in November, right?)