Rubio appeared on ABC’s This Week yesterday and said this  about normalization with Cuba:
We have those policies of normalization toward Vietnam, for example, toward China. They’re not any more politically free today than they were when that normalization happened. They may have a bigger economy, but their political freedoms, certainly I would not hold up China or Saudi Arabia or Vietnam as examples of political freedom, proving my point, that engagement by itself does not guarantee or even lead to political freedoms.
It’s true that diplomatic engagement does not necessarily guarantee or lead to political freedoms in the other country, but we know very well that refusing to engage with authoritarian regimes ensures that there is even less of a chance that political liberalization will occur. While China and Vietnam are not noticeably freer politically now than they were before the U.S. established normal relations with their governments, no one in the U.S. today would seriously argue that normalizing relations with either of them was a mistake or that the policy should be changed back to what it used to be. The central flaw in Rubio’s argument is his assumption that the U.S. must not resume relations with another country until its political system has started liberalizing. That holds normalization with Cuba to a standard that the U.S. has never applied anywhere else, and treats Cuba as if it were unique in having a repressive government when everyone can see that this is not the case at all.
Even if nothing changes in the Cuban political system for the better for the next twenty years, both Cubans and Americans would still be better off from resuming diplomatic ties and substantially increasing trade. No one can credibly argue that the same would be true if the U.S. continued the old policy for that period of time. It may take a long time for renewed relations and increased trade to have any meaningful effect on Cuba’s politics, but that is all the more reason to start the process now. In order for Rubio’s argument to make the least bit of sense, one has to believe that continuing a policy of deprivation and punitive measures can have liberalizing effects after decades of not having had any. That is an obviously absurd thing to believe. Rubio wants to keep cutting off one of our closest neighbors from engaging in commerce and diplomacy with America, and he wants to be applauded for his dedication to freedom. He can have one or the other, but he doesn’t get to have both.