Historical narratives matter. That's why conservatives are still writing books denouncing F.D.R. and the New Deal; they understand that the way Americans perceive bygone eras, even eras from the seemingly distant past, affects politics today.
And it's also why the furor over Barack Obama's praise for Ronald Reagan is not, as some think, overblown. The fact is that how we talk about the Reagan era still matters immensely for American politics.