Its almost impossible to take out an incumbent unless things are going bad. Goldwater didnt lose because he was conservative, he lost because in 1964 LBJ was very popular. By 1968 LBJ was practically run out of town.
JFK was in Dallas that fateful day, because even with LBJ's fine Italian hand directing the voter fraud, JFK would have lost BIG TIME the next year.
Run out of town?
LBJ was unpopular with radical college students and white southerners more than anyone else
When he announced he would not seek or accept the Democrat nomination folks were shocked
He sure wasn’t run out of town not by a long shot
All polls indicated he would win reelection
Many of the insiders have written on this and blame Vietnam....he chose not to run again cause he was burned out and felt he’d wasted a lot of lives frustrated by a wily foe and weak media plus his heart disease was gaining on him
I still remember when he announced...it was unexpected
He was frustrated with the war he was personally managing and the media sentiment
In the interest of accuracy I’ve pinged someone smarter than I on modern history in case I’m way off but it’s how I recall it as a kid