This scenario has the electorate knowing what would happen if Nixon and Agnew were reelected, but not knowing what would happen if McGovern and Shriver were elected.
If the electorate knew that Agnew would be forced to resign in disgrace after details of his accepting bribes, as Governor of Maryland, became public, and that the President himself, Richard Nixon, would be forced to resign, or face inevitable impeachment, for subverting the constitution and violating his oath of office, and bringing the nation to a constitutional crisis, with cover ups, bribery, extortion, intimidation, threats, and having such slimy characters as Mitchell, Haldeman, and Erlichman, among others, high up in positions of power and influence in the administration, I hardly think that anyone in their right minds would reelect Nixon and Agnew under these circumstances.
McGovern and Shriver win this election by a huge landslide, dare I say sweeping the nation, as the electorate reacts with disgust and anger at the Nixon and Agnew behavior.
They would take their chances with McGovern, and hope for the best.