If the truth about Watergate came out 6 months earlier than it did ... and Muskie & Ted Kennedy we’re together on the Democratic ticket, I think Democrats could have won. Despite Chappiquidick and Nixon’s favorable up to that point.
What does "the truth" mean?
If the full truth came out, Nixon probably would've had to resign as he eventually did. Democrats probably could've beaten Agnew; it's true. But Watergate was already being reported before election day 1972, and Nixon won as he did.
The truth meaning that Nixon knew of it soon after it happened and so on. He won in 72 but prevailing wisdom at the time of the election was that it was low level people that was totally unrelated to Nixon.
If Watergate truth comes out before October of ‘72 then both Teddy and Muskie would have beaten him IMO. Muskie decively, Teddy decively without Chappiquidick & narrowly with it.