It was in California, after Roosevelt died, that Ronald Reagan started to rethink his position when it comes to politics. When he was an actor, he got involved with the Screen Actors Guild and even became president of this actors’ union. It didn't take too long for him to become disillusioned by some of the bullying tactics (even against him physically) of the labor movement. Besides that, his slowly shifting political philosophy was also nudged along when he found himself paying 90% of his earnings in taxes.
Reagan had been a Democrat until 1962, when he became a conservative and switched to the Republican Party, in 1964.