http://www.indyweek.com/indyweek/from-nixon-to-trump-the-parallels-between-1968-and-2016/Content?oid=5086105
I am almost 50, and so only barely remember the political divisions regarding the Vietnam War and then Richard Nixon. My MIL, who accompanied me to the Mall on Saturday, said that she participated in the 1968 Chicago protests. The article cited above theorizes that just as the civil rights, women's movement, and endless foreign wars created a traditionalists vs. progressives split that gave rise to Nixon, similar conditions existed in this election cycle.
My fear is that unlike the Nixon era, which had Nixon vs. a Democrat-controlled Congress---Trump is completely unfettered, as the GOP has shown that it is willing to overlook anything in order to keep power (and from alienating Trump's populist supporters).