If you are to predict who will be the GOP nominee?
My bet is Rubio. If he wins the nominations, he could also win the presidency; Hispanic votes; New Mexico, Florida, Nevada etc. He could even have a slim chance of winning California. I know that he is Cuban American but hispanics will vote for him; the first Hispanic president.
Ben C is becoming like Herman C. He will be leading for a few more months and fade.
I'd say Rubio. He's young, he's going to be backed by the establishment with Bush fading away, he's still newish to Washington DC (only been Senator since January 2011, just one term), and he will appeal to Latinos.
He won't win California, the Clinton machine is still very powerful. But Florida is in play. Nevada and New Mexico I'd say still lean blue but Colorado could be at play.
Rubio would be Hilary's toughest challenge in the generals.
Jeb Bush was the frontrunner who was strong that he scared Mitt Romney away; the Republican nomination was his for the taking and complacency slowly set in, then this happened:
Once the campaign began in earnest, however, it became clear that Bush was more than just rusty from having not run a campaign in more than a decade. He was simply underwhelming at every turn. In each of the first two debates, while far less experienced pols such as Rubio, Donald Trump, Carly Fiorina and Ted Cruz outshone Bush, his allies sifted through the scraps of the debate in search of signs of life. He said his brother had kept the country safe! He was the grownup on stage! They insisted that Bush just needed to keep improving in each debate. He would never be the performer that Rubio and Cruz are but he didn't have to be. He was Jeb, after all.
Those voices went silent after his flop in Boulder. (Sidebar: When your best argument is that you didn't get enough time to talk and your last name is "Bush," you are losing.) There is simply no way to spin what happened. Bush tried to do what his advisers told him he needed to. It didn't work. In fact, it backfired badly. He spent the rest of the debate in the shadow of that failure.
Weak campaigning skills, weak public speaking, no fire-in-the-belly, no appetite for retail politicking; he assumed he would win the nomination on the strength of his last name, his record-breaking fund-raising(also, due to his last name), and his governing record on Florida. But then Donald Trump happened. And Ben Carson happened. And Marco Rubio happened. The first two are 100% unelectable, so Rubio wins by default.
Rubio is running the most disciplined campaign in either party; he also is the most talented public speaker of the 2016 race in either party. I agree with Lama & Fah, he wins the Repub nomination. Hillary's in a for a tough race.