1980, as this was the first election other than '72 where the Democrats started really losing the FDR/Truman Democrats. The malaise of the late 70s and the deindustrialization that occurred as a result of international competition utterly discredited the post war Liberal order. Nixon arguably ran to defend that order against the New Left in '72, and ran as someone who could run that Order more effectively in '68. Reagan ran to overturn that order and pointed to the failure of Carter (and this was a trend also seen in Britain when Thatcher triumphed over the incompetent Callaghan government because of the constant labor militancy that terrified people) as a way to point to something else.
Nixon was a Cold War conservative liberal, and arguably was a national conservative as well. Reagan was a movement conservative.
The rise of Reaganism and movement conservatism was a direct reaction to the collapse of the FDR liberal order and the rise of the New Left. Nixon still operated within the confines of the liberal order and upheld it through his actions. He did not try to roll back the state like Reagan did. Reagan instead revolutionized the status quo of the American government. Clinton, Bush, and Obama all upheld Reaganism to different extents.
Trump has indicated going in a different direction on issues like trade and immigration, seemingly more like a remnant of the Old Old Old American Right of Calvin Coolidge rather than the Alt Right, but by and large, his appointments and actions so far indicate someone who would like to fuse the National Conservatism of Nixon within the core confines of modern day movement conservatism.