This doesn't explain the Nixon re-election landslide, amongst other election results. Everyone hated his guts, but they at least respected him for being competent (outside of Vietnam), whereas Agnew was viewed as a near-commie menace and not a heavyweight. They basically held their nose and voted for tricky Dicky. Voters will generally prefer someone they dislike but who they think has sufficient stature for office, versus a likeable but unsound lightweight.
Can you possibly point to any poll from the time that supports this statement? I just can't fathom that this statement is correct, but I will give you the benefit of the doubt.