It is possible that Jeb will turn out to be too embarrassing a candidate for the Bush family and Jeb will be induced to drop out in which case Rubio is supposed to become the RNC candidate and nominee. Even someone like Kasich is not completely out of the picture as Rubio may be making himself obnoxious to the Bushes and thereby to the RNC. Rubio's job was to collect conservative base votes- and not steal gope votes from Bush- and then bow out handing his delegates over to Bush. Rubio has deviated from the script and that may not be acceptable to the RNC.
The truth of the matter is that overall polls are pretty accurate. Right now and we are getting pretty close to the voting Trump is topping all the polls and absent an alien abduction he will be the nominee whether he wins Iowa or not.
Starting next week we will be in the holiday season and traditionally voters do not pay much attention to politics until after Jan 1st. By then it will be so close to the Iowa caucus and NH then SC a contender will have no time to catch up.