If Rand is "allowed" to win the GOP nomination, he'll be slaughtered by the Democrat nominee in the November 2016 general election. Most non-Whites vote Democrat anyway, but almost all of the ones who would consider voting Republican will be scared out of doing so because Paul will be portrayed as wanting to greatly slash government spending on social security, welfare and other social programs. And so that leaves Rand only the increasingly smaller White base of the GOP that the party is ashamed of and won't appeal to under any circumstances, so most Whites with liberal leanings or who are on government assistance of one kind or another (which is a lot of Whites these days) will vote Democrat out of self-interest. It will be a repeat of 1964 no matter how bad things are in the country, assuming all hell hasn't broken out by then.
The Republican Party's only hope is to rally its White base while it's still a majority, but that will never happen. Rand Paul is just as bad as any of them on race and immigration, so it doesn't really matter, the two-party system is a one-party system and that is the only important issue. The end result of the GOP supporting third world immigration, free trade, outsourcing and open borders is that the GOP is very close to the point, if not already there, that it will never again win the presidency. And more and more big population states are going irreversibly Democrat at the state level thanks to demographic changes and two generations of cultural communist indoctrination.
Maybe a "conservative" Republican like Jeb Bush will be able to win one more presidential election, but really who cares? It's a unitary power structure.