I think we can rule out Hiram Johnson. For his reaction to the offer of the vice-presidential nomination, see David Pietrusza, 1920: The Year of Six Presidents, pp. 237-8:
"Hiram Johnson took it [defeat for the presidential nomination] less well [than Leonard Wood]; but then again, Hiram Johnson probably would have taken victory with ill grace. With his wife and son and secretary, he sat sulking in his Hotel Blackstone rooms. Popular poet James J. "Jimmy" Montague, a close Johnson friend, phoned Irvin Cobb and Ring Lardner: "Come along down to the Blackstone, we're going to sit shivah with the Johnsons. They need company."
"The gloom was intense, and someone opened a bottle of scotch. The phone rang. Johnson's secretary answered. It was Teddy Roosevelt Jr. Johnson knew he was calling to persuade Johnson about the vice-presidency. Everyone in Johnson's suite knew that that would be the only reason Roosevelt would call.
""Tell him I'm not swapping idle conversation with anybody this evening," Johnson fumed. "Tell him I've gone to bed-—tell him anything."
""Hiram," Johnson's wife urged, "for his father's sake if for no other reason, you must listen to him. And he's a fine boy and I'm fond of him. So are you." "This is no time for sentiment," Johnson spat out. "I'm more in a mood for murdering a few people."
"He took the call. “Hello, hello. . . . Johnson speaking. . . . No . . . no, not in a million years. . . . No, I tell you, no. . . . Oh, yes. . . . No, sirree. . . . For the last time, damn it to hell, NO!" Then, face reddened by rage more than Scotch, he hung up--hard.
"Montague had a question. “Senator, there wasn't any doubt as to what you meant by all those 'noes,'” he asked, “But that solitary 'yes' in the middle of 'em-—just here in the bosom of the family, would you mind telling us why you stuck in that lone 'yes'?”
"“Oh, that?” Johnson responded, his mood finally lightening. “That was when the young man asked me if I was sure I heard what he was saying.”"