Ike.
If Nixon had the full backing of the incumbent, with all his power and lever-pulling, of course he would have challenged. But I don't think he could count on Ike to help him in any way. Think back to 2000: I can't recall any instances where Clinton really worked to help Gore in the challenge.
I’ve never thought about it before but you’re right, I don’t remember Clinton helping Gore.
Everything I’ve read said Ike took 1960 hard, almost like a personal insult that Nixon didn’t win his ‘third term’ for him. You’d think that would mean he would have favored a challenge. I guess he didn’t want to ‘divide the country’ with it.