In retrospect, which were realigning elections?

[Roronoa D. Law]

1968 - The switch between the south and the north voting patterns still relevant to this day

1992 - First sign of Democrats appealing to suburbanites and the new minorities of Hispanics and Asians. Westchester NY, Ventura CA, Montgomery PA, Broward FL, and St Louis County MO all flipped. These where major suburban counties that were the birthplace of Republican Conservatism and every major urban and suburban county has followed suit after this election. 

[Roronoa D. Law]

Surprised so few people chose 2000.  That was the election that really pushes the GOP rapidly towards its current appalling path culminating in Trump.  In many ways, GWB and his cronies were far worse than Trump because they set this in motion.

If you mean when did the GOP went looney then that started with 1994 with Gingrich and the rise of Fox news.

There was a clear indication that Republicans where gaining ground in the south as early as 1968. Carter and Clinton were only able to stop bleeding because they were from the South. We didn't see Democrats starting winning the NE and West on the backs of suburban women and minorities till 1992.