Obama hasn't endorsed anyone because he wanted the voters to decide, on their own. He did not wish to be a "kingmaker".
Bullshit.
I've never heard of a former President not endorsing his VP.
JFK never endorsed LBJ. Fact.
I'm going to give you a funny...because I lol'd...but it's kinda sad too.
Dark humor. But TROO!
FDR never endorsed Truman either, and I don't think he would have.
Anyway, it's way early for an endorsement. First guy I looked up was Eisenhower, knowing how little he thought of Nixon. Ike did give an endosement --- in July.
All before my time...Nixon was president when I was born...but I don't remember him or Ford...Jimmy Carter is the first President I remember. The Oil Embargo, gas lines, solar heat in the White House and Hostages in Iran.
Omigod, you're a young whippersnapper? Here all this time I thought you were an old fart. Musta been the previous avatar. I do remember Eisenhower from childhood (mine, not his).
Reading up on it a bit it turns out the reason Ike did that endorsement in July, more than two weeks before the party's convention, was because he was in Walter Reed having heart attacks every other day so he broke with his tradition of never offering an endorsement before the party formally nominated somebody, fearing he wouldn't survive that long. Still don't know for sure about 1960 but he clearly danced around it.