Soviet influence in Cold War American politics?

[Luigi]

Im not much of a CT guy but today I heard one that is fairly believable yet I had never thought of it before or realized how significant it could be. The idea is that during the Cold War the Soviet Union was sending funding and agents to American political movements to facilitate the growth of communism and instill rapid change and destabilize American society to make it more dissatisfied with the capitalist norm. This in turn led to the radical changes in American politics at the time(mostly movements towards the political left).

Considering it is a well known fact that the FBI and CIA were FULL of KGB spies for most of the Cold War, I have absolutely no problem believing this CT.

Thoughts?