This one, admittedly, is a bit of a hard sell. Between the Vietnam War, Johnson's harsh personality, his failing health and his growing impopularity within both the Democratic Party and the American Public, dropping out of the 1968 race probably saved him from a sound defeat against Nixon in 68. Effectively, LBJ is in a situation not unlike that of Truman in 52 (truly irreversible, unlike Truman in 48), so PODs and plausibility thereof are less of a priority here, although having LBJ face someone like Goldwater or Romney might perhaps help, who knows.
So, for the sake of argument, assuming Johnson could survive the primaries thanks to the party bosses and structure, and the general election due to a bad opposition, where does that leave a second/third Johnson term? Assuming Peace in Vietnam is what saves him in 68, where does that leave the rest of his foreign policy? And where does an extra term for a weakened, tired Johnson leave his once ambitious and transformative domestic policy, now that half of America is on fire, and so is the Democratic Party?
So, for the sake of argument, assuming Johnson could survive the primaries thanks to the party bosses and structure, and the general election due to a bad opposition, where does that leave a second/third Johnson term? Assuming Peace in Vietnam is what saves him in 68, where does that leave the rest of his foreign policy? And where does an extra term for a weakened, tired Johnson leave his once ambitious and transformative domestic policy, now that half of America is on fire, and so is the Democratic Party?