If Watergate never surfaced and Nixon wasn't term-limited, he would have won a third term handily (possibly against another Democrat because Carter only became the nominee as a result of Watergate). If he was term-limited, John Connally wins the election by a fair margin but is a one-termer during the many difficulties in the 1977-81 term and Republican third term fatigue. 1980 has a ticket like Reubin Askew/John Glenn elected in a landslide. All this would have been way better for America going forward with no Carter and no Reagan.
OP said Watergate still happened in this scenario, so I assumed it still surfaced. I don't think Carter would have been incompetent enough to ignore such a huge scandal if this scenario had actually happened... hence why I have Carter winning in a massive landslide.