His Speculation is Predicated on a Major Presumption …
… namely, the quality of his own presidency.
From the Telegraph (UK):
Standing in his cowboy boots on the back of a 1941 Ford pick-up truck in tiny Zebulon (population: 4,329), Bill Clinton bestowed on his wife Hillary what he perhaps considers the ultimate accolade. She would, he stated gallantly, be an even better president than he was.