Actually .... just to throw another spanner in the works in a campaign that's already had its fair share of twists, we have the stalking spectre of Michael Bloomberg to consider
If he enters as an independent his price will halve on the spot
He's weighing up whether there is a gap in the market. At the moment he can probably be confident that the Republicans are putting up a dangerous and divisive hawk who is going to be completely unacceptable to a whole swathe of America. On the other hand he has to consider whether he could beat Hillary who might look a bit wounded by March when he's promised to make a decision.
Despite having been a Republican Mayor of New York, there is a fair chance he'll pick up Democrat votes too, and could easily do them more damage in California and the North East seaboard.
Gatecrashers and New York Mayors have a lousy record. He couldn't win based on history, but there is a fair chance that in a campaign that has been dominated by a sense of crisis amongst the political establishment America might suddenly look at a shootout of Trump/ Cruz versus Clinton and be crying out for a middle ground alternative to save them from themselves. At the very least he'd alter the dynamics of the race, perhaps decisively
Will he run? My best guess is he wont, but money is no object, and there's plenty of plausible scenarios that might encourage him to. The obvious one would be a polarising Trump v's Sanders race which leaves a big middle ground he could conceivably take. I think he would be tempted if that starts to unfold. He'll know that America's natural heartbeat probably doesn't lie comfortably with either.
Bloomberg might be a Republican on paper but his policies are nearer to Hillary's than anything coming out of the GOP. If she begins a recovery after the two early rounds he'll probbaly keep out, but if he sees Sanders gaining ground I think he'll be persuaded. Will Bernie get momentum that he carries through into South Carolina and Nevada? or will New Hampshire represent peak Sanders? Hillary could trade Iowa for New Hampshire, but losing both would at least draw Bloomberg a step closer. As a well resourced independent of means remember, he doesn't need to appease a primary season seeking a nomination and could cut straight to the campaign
If Hillary loses Iowa, the smart bet might be anm immediate stake on Bloomberg before the market reacts
