As Hunter Thompson portrayed it in his least factual, most accurate account, the 1972 Democratic race was a fair bit of a horse race. It was made all the more interesting since the Democrats were likely to lose in 1972, so it was a scramble for a sinking ship. And it involved the older guard who had crashed and burned over the course of the 1960s, the New Left and new forces which were taking over the party, and Nixon exploiting it and picking up whatever was left over to make more Republicans. Going into 1972, many people wanted Humphrey back. Barring him, his former running mate Edmund Muskie was widely viewed as the front runner. However, Muskie's campaign imploded (due partially to Nixon, Hunter Thompson, and assorted other factors). That allowed McGovern to win the nomination, despite the establishment not wanting him. Subsequently, they did not vote for him, and Nixon won one of the biggest landslides in American history.
What if Edmund Muskie had been the Democratic nominee in 1972?