Democrats
Sanders - a genuine old-line honest socialist, American version. Has the virtue of sincerity, and is not "focus group tested." His views are as close to those generally accepted in Merseyside as any actual American politician that you are ever going to see taken seriously for the job. Would win the English vote in a walkover. Will have serious problems with the ethnic vote and women, which will need to turn out in spectacular numbers for him to win the general.
Clinton - Tracy Flick at age 68. Married to one of America's best retail politicians ever. Hasn't said a spontaneous non focus group tested word since 1993. She believes and supports whatever she thinks she needs to believe to win - she's Blair in a pantsuit that way. Must get a huge turnout of the women's vote and a repeat of the kind of black/hispanic vote turnout Obama got to win twice. [This individual doesn't think she'll make it to the nomination for a bunch of reasons. Will likely withdraw for "health reasons" unless she wins through the primaries and dodges all the ongoing investigations. 100 agents full-time and 50 agents part-time are currently working on the FBI probe of much more than just her emails.
Obama's justice department will eventually decide whether she skips through this or not. Joe Biden will have to cure cancer and run for President all at the same time. You heard it here first... (maybe).]
Republicans
Trump - go read up on Scott Adams' (Dilbert's creator) thoughts on Trump. I think he comes closest to figuring out the mysterious (to me) appeal. Scott's not your average cartoonist.
http://blog.dilbert.com/post/137089875456/the-oddest-thing-about-trump
Cruz - The thinking angry man's candidate, and the choice of Republican evangelicals and angry non-Trumpets. Alan Dershowitz says he might be the smartest guy he's ever seen go through Harvard Law. A masterful debater and creative strategist, he doesn't care what the boys in DC think, and is running against the institutional Republican party and the federal government in general. Most folks in L4 would think he's from another planet, but you'd best take him very seriously. He has gone much farther faster than I thought he would in this race.
Rubio - He's as good on the tube as some kind of Obama/Blair mashup. Looks like a combination of Slater and Zach, all grown up now. Thinks well on his feet, and has an appealing immigrant story for his own background. Is seen by the Trumpkins as an unreliable candidate due to his former friendliness to efforts to do a comprehensive immigration deal with the Democrats, in which he got his pants taken down, reversed, and the pockets cut out by Chuck Schumer. I marvel at the fact that he is now seen as the establishment candidate with the best chance, as he got into the Senate as a Tea Party insurgent while running against Charlie Crist, America's most flexible and least principled politician.
Nobody else has a chance (with the exception noted above), take it from me.
History would indicate that it will be exceedingly difficult for the Democrats to pick up a third consecutive term with Obama's popularity numbers as low as they currently are. The Trump phenomenon may blow up all conventional expectations, however.
To paraphrase what a former PM said back when dinosaurs roamed the earth, we are at the mercy of "events, dear readers, events..."