The election of Ronald Reagan in 1980 provides the best recent precedent for the unexpected triumph of Donald Trump (in my opinion, the other post-war Republican takeovers of the White House -- Ike in '52, Nixon '68, and W. in '00 - did not constitute a real break from the status quo.) As many people expect great changes from Trump, it is worthwhile to look at what the Reagan Revolution actually wrought.
Both Reagan and Trump were better known to many as entertainers rather than politicians, both came from outside the Republican mainstream, and both engineered hostile takeovers of the Party. During the 1970s, the Republican Party was dominated by "Rockefeller Republicans," the Ivy League-educated liberal Eastern elites. Reagan was the Western heir apparent to Barry Goldwater, the deeply conservative standard-bearer who went down in flames in 1964. In 1976, the brash Reagan had the nerve to challenge incumbent Republican President Gerry Ford in the primary, thereby weakening him in the general election, which he ultimately lost to Jimmy Carter. While Reagan was simply too conservative for the Rockefeller wing, Trump's various positions are similarly inconsistent with much of the mainstream neo-conservative orthodoxy. Both candidates also capitalized on a weak economy as a catalyst to encourage voters to cross traditional party lines. Many of the rust belt "Reagan Democrats" came home to Trump.