Come 2016 it is very likely that the three most likely front runners for the Republican nomination will be (in no particular order) Paul Ryan, Rand Paul and Marco Rubio. There will probably be be others, Chris Christie being a strong possibility but as it stands right now those three have the inside track to be the favorites.
In that likely scenario Paul Ryan and Marco Rubio will be considered the "establishment candidates" and Rand Paul would be considered the "grass roots" candidate. Think about that for a minute! Consider how far to the right the Republican Party has shifted in the past five years to even have such dynamic conservatives considered the front runners.
Think of the optics of those three being the front runners and for all practical purposes the spokesmen for the GOP debating one another on the national stage. If people like (my personal favorite) Mike Pence get into the race or even a woman or two like Susan Martinez or Kelly Ayotte jump in, the field would indeed be quite impressive. The mere fact that the only RINO on the list of serious potential candidates is Christie just goes to show how far the Republican Party has been shifted towards the conservative view.