It was the 1974 Midterm election that was a bloodbath for GOP.
In 1976, Carter’s narrow victory over Gerald Ford had limited coattails, and his Democratic Party gained a net of only one seat from the Republican Party in the House. This election is notable for being the last time any party had a veto-proof majority in the House.
There really is a lot online including the network election night coverage which is fascinating. Every Midterm and Presidential election since 1948 is on youtube. You could also just wiki the election in question as they are generally accurate with regard to publicly available election results. GOP suffered landslide lost in Congress in ‘74 after Nixon resignation on Aug 9. In ‘76 Carter narrowly won presidency. Reagon then won in 1980 with a 45 State Landslide and picked up 13 seats in Senate.