Johnson wasn't. He said "to hell with it" after his bad primary showing in New Hampshire and left the field. Not that it did McCarthy any good because Humphrey got the nod.
The reality is closer to what happened in 1976 when Reagan challenged Ford and then four years later when Kennedy challenged Carter.
I have been very interested in Reagan's 1976 challenge because I have been hypothesizing what the world might look like today if Reagan had defeated Ford. No Iranian revolution, for one thing, but I digress...
For all that he was a hero, Ford was also as dull as dishwater, had microscopically thin support outside of Michigan and was burdened with the odium (to the left) of having pardoned Nixon and (to the right) of signing the Helsinki Accords. He did however, have the Big Blue Bird, all the trappings of office and the other advantages that incumbants enjoy.
But therein lies my point. The office itself conveys enormous advantages and gravitas on the incumbent that make it very unlikely that Obama would lose the nomination if he decides to fight for it down to the convention.
He might not. I could easily see him doing a "Johnson" and bailing out early.
Good points you make there, and I considered carefully what you said in your preference to liken the 2012 demo primary possibility to the 1976 and 1980 unsuccessful sitting-president primary challenges, rather than to the 1968 (and 1952) successful sitting-president primary challenges.
Consider:
You said: “I said “no primary challenge to Barry has a realistic chance of succeeding if he’s determined to keep the Oval Office”.
Apparently you meant to say “determined to take it all the way to the convention floor.”
You said: “Johnson wasn’t. He said “to hell with it” after his bad primary showing in New Hampshire and left the field.”
Johnson was exceeded by no one in his determination to seek and hold power. Johnson was only acknowledging political reality after the stunning primary results and then after Bobby jumped in, he knew his fate was sealed. Johnson’s failure to back Humphrey was incomprehensible unless Johnson held out hope for a deadlocked convention in which he would be asked to save the party, but the ‘68 Chicago convention in Chicago where the party was essentially taken over by the student radicals and anti-war movement made that impossible.
The likely scenario I see happening to Obama is the challenge from the left, by some young charismatic egotist, announcing sometime this fall, especially if the wars expand in the middle-east and the economy tanks. I’m just seeing cracks in Obama’s support and slim chances of his approval numbers getting better, which is what leads to a candidate deciding, or being told, to bail out like happened in 1952 and 1968.