Looking at the starting map (on impossible), MA, RI, DC and HI already are the only states more democratic-leaning than tossup. And according to here at least, https://en.wikipedia.org/wiki/Historical_polling_for_United_States_presidential_elections , in early 68 Nixon had a more modest lead over Humphrey, of at most around 9%, and with Humphrey leading at times. And after the convention, with Humphrey at his lowest point, Nixon had at most around a 16% lead, not ~quite~ a 20% lead. Though I can still see a case for it being a bit too easy