Question

What new assumptions did kennedy and johnson make about the proper role of government

Answer 1

In general, both Kennedy and Johnson assumed that government could play a large role in the political and social affairs of states. This is how they enforced Civil Rights legislation.

Answer 2

They supported the idea that the government could do a lot more to help people economically and socially than it already did. That's why they supported introducing the civil rights act on a federal level, and various other such laws such as healthcare. They didn't want to let individual local state governments handle this because they wouldn't want to do it.