If he had any balls he would answer the question honestly. His big money donors told him they wanted amnesty, and Schumer and McCain assured him the bulk of his constituents would get over their anger enough to vote for him in the next election. That, and he could expect an influx of campaign donations from the big money donors, enough to give him a substantial advantage over a challenger.
politicians are never honest.
Nothing in politics is honest.
Bingo! McCan't and Grahamnesty used him for their purposes and I'm sure enjoyed discrediting a Tea Party favorite in the process. Rubio, however intelligent he may be, showed lack of common sense in getting suckered in by this.