Why did Ronald Reagan switch from a Democrat to a Republican? [View all]

I have been reading a bit about Ronald Reagan and I was surprised to find out that he was a Democrat in his younger years. Reagan was a big supporter of FDR and the New Deal and was very pro-union. Regan was even president of the Screen Actors Guild. But Reagan would eventually become a Republican in 1962 and supported Barry Goldwater in 1964.

I have read all sorts of reasons for Reagan changing parties, everything from making more money and getting hit with higher marginal tax rates to his stint working as a spokesman for General Electric.

Why do you think Reagan changed parties and ideology?