Cuban-Americans are immensely loyal republican voters, they will overlook a lot of stuff and they have a tendency of voting regularly, if they don't like an issue and there is reason to believe that they may switch sides (extremely unlikely) or that they won't vote, then for a state like florida which has had the tendency of playing hugely in past presidential elections, then this stance might help GOP reconsider their positions if they want to win the next presidential election. Recall... Al Gore lost his presidential elections due to a few hundred votes in Florida.

BTW, the governor race was extremely close, I believe it was 51% republican, as for the senate race, Rubio did have very strong arguments across the board, it was not just on immigration that he won, and he did have to soften his immigration stance somewhat.