LBJ couldn’t run because of Vietnam. How that advanced his interests, I don’t know.
Despite his leftism, LBJ didn't want to tear the country apart; he merely wanted to secure long term democrat control over government and the electorate. He couldn't run precisely because society was divided over the war.
Obama himself has said he would rather be a significant one term president...and at the risk of straying into tinfoil territory, he didn't say how long that term might be. I know we talked about it during Clinton and Y2K, and admittedly the left talked about Bush suspending elections due to the WOT or other national crisis. I'm not saying Obama will suspend elections in 2012 (or 2016), but I do believe he'd have no problem whatsoever trying it if he believed he could get away with it. The bigger the external crisis and the more desperate the domestic situation, the easier it will be for him to get away with it.