Reagan was a realigning President. The reason why that wasn't as obvious as it was in say FDR's case is because Tip O'Neill and the Democrats were able to adapt to the new era and work with Reagan whereas the Republicans in the 30's and 40's still fought against FDR's New Deal programs tooth and nail out of sheer stupidity.
The 1994 Republican Revolution made it clear that Reagan had been a realigning President. As does the fact that he created a political environment which forced the opposition Party to moderate drastically to survive. Bill Clinton was forced to govern more like Reagan did than LBJ. Clinton cut the capital gains tax rate, deregulated, supported free trade deals, pushed for tough on crime laws, ended welfare as we know it, etc.
Realigning Presidents are usually succeeded by their own Party (Lincoln, FDR, Reagan) so Bush losing in 1988 would be a huge sign that Reagan didn't actually end the FDR era and become a truly transformative figure in American politics.
That kinda is what sucks about the dems now is that we could be nearing a dem realignment what with the trending suburbs/Milenials entering the middle class/ growing diversity/Trump as president with Obama legacy as the guy who had to take the heat to open the door to the democratic Reagan but I don't see a Reagan out of this bunch (not to say they can't beat Donald which of course is possible an borderline likely at the rate he's going) but the realignment guy I don't see. What I wouldn't give for Jerry Brown to be 30 years younger.