Nancy Reagan. She approached the Screen Actor's Guild president, Ronald Reagan for help clearing her maiden name. That's how they met.
There WAS a Communist actress named Nancy Davis. No one in government was involved. And McCarthy had not even made his Wheeling speech yet.
Well, technically, McCarthy wasn’t actually involved in Hollywood’s blacklisting and crackdowns on Communist agitators (he was strictly focusing on stuff within the Senate’s jurisdiction. That’s also why we shouldn’t attribute HUAC to him either, since that falls under the House of Representatives), so even if Nancy Reagan was falsely accused, McCarthy wasn’t wrong about her since he was never even involved in her accusation in the first place.