Rubio is who the establishment wants to be their nominee but I don't see a path to victory for him, where is he going to win? He's in 3rd in home state which is better than Jeb I guess who is battling for 4th with Carson. Even if you add up all the support of the favored establishment candidates into one candidate, they would barely eek by Cruz. Christie might have some base of support in the northeast and is more of a combative personality, I think Christie could overtake Rubio as the establishment choice if he finishes well in New Hampshire. Rubio is too married to amnesty to have any chance at winning with this GOP electorate, same with Jeb on top of being a massive dork.
It's Trump's race to lose at this point, somebody has to actually beat him and I don't see anybody in the race right now being able to do it. Trump's support is much broader and more diverse than any other candidate, he leads every demographic, his support is much more intense than anyone else, and remember Trump has barely spent any money at all. North, south, east, west, Trump is not a regional candidate. It has actually been speculated that Trump's support has been underestimated because polling only works when voters are predictable which Trump supporters are anything but, these big polling companies are dinosaurs who still work landlines. If Trump is actually attracting support from outside the traditional political spectrum as so many are saying then we won't know the extent of his support until they turn out at the polls. Bringing new people into the primary process is how you win, Obama was able to do this in 2008 to overcome the Clinton machine. Ron Paul to a lesser extent was able to do this as well bringing young people and others traditionally scorned by the GOP establishment, he was a sneeze away from winning Iowa. Old media doesn't control the narrative anymore, more and more people get their information from the internet and don't trust the talking heads of cable news.
The black vote might go as a bloc but Hispanics are not a monolithic grouping and don't vote that way, I don't think it is likely that GOP will lose with them any worse than they did with Romney. Hispanics that still support the Republican party actually support the Republican party so there is no need to change, some of the most anti-illegal immigrant people I know here in Arizona are actually Hispanic themselves believe it or not. The only people at really support this invasion are big business, white-guilted liberals, and Democratic partisans. The party that claims to support poor people sure likes to make their lives harder, especially poor minorities who suffer the most from illegal immigration. I mentioned this before but the great Mexican-American labor activist Caesar Chavez was actually the first person to lead "Minuteman" border militias aimed at stopping illegals all the way back in the 60s since he considered them scab workers which they essentially are.