Reagan's approval rating low was 35% in January 1983. Bush the Elder was 29% in July 1992. Clinton was 37% in June 1993. Bush the Younger was 25% in October 2008.
Congressional Republicans currently have a 22% approval rating, Democrats are at 33%.
Much of the 78% must be folks who can't stand the Boehner's/Cantor's/McCarthy's/McConnell's, and would give higher approval if only there were more Cruz's/Gowdy's/Gohmert's/Paul's.