The way things are with US elections right now, anyone can enter primaries as whatever party they choose. Because of the open nature of most primaries and caucuses, if someone wishes to seek elective office all they need to do is proclaim themselves a Democrat or Republican and do their level best to entice the public into supporting them rather than appeal to the respective party on the grounds of political philosophy. As almost anyone can vote in the primary or caucus of their choice in order to select candidates for either major party. The parties have increasingly little say in who actually represents them.
What this does more than anything is weaken party identification and, in the end, any real choice we have in who we elect. It leads to what currently are called RINOS: Republicans in name only. One would supposed that DINOS, Democrats in name only, would be rampant in the political world as well. Basically we end up with two parties: Demopublicans and Republicrats, political movements of a hash which leave little save bland taste.
As political parties are essentially private entities, it should follow that they ought to be able to select their own candidates for office. It would create something more akin to what parliamentary systems have, a party discipline wherein you could not run as a Republican or Democrat unless you really stood for what the party did.
What we require is a return to the smoke filled rooms of yesteryear. That would stand a better chance of giving us as the electorate a real choice in who becomes our legislators, congressmen, governors, and presidents. Let the parties choose who represents what they believe in. Then we may actually see a difference in the GOP and the donkeys. Until then, we shall get what we deserve: bad philosophy, and worse politics.