If McGovern doesn't run in 1972, then some other farther-left Democrat will. Anti-war sentiment was very strong among non-Southern Democrats in 1972, and delegate selection rules had been drastically reformed to reduce the dominance of traditional party insiders. This process had gone so far that the convention expelled the entire Daley-led Illinois delegation because there weren't enough black & female delegates, and instead seated a delegation of liberal reformers that was actually far less representative of Illinois Democrats than even Daley's group.
The McGovernite leftists believed that their views would carry the day in November, that America was truly ripe for a truly "progressive" political program; but, like the Goldwaterites in 1964, they'd overreached & lost big time. By 1976, the Democrats were less interested in ideological purity than winning.
Your point is very good. The Democratic Party outside the South wanted a radical antiwar program but the voting public, and perhaps even the nonvoting public, found it too extreme.
It is
just to criticize the Democratic Party’s identity politics because of its failure to improve living standards for blacks and other non-whites, and even for lower- and middle-class whites.
However, the hostility of white working-class and
petit-bourgeois America to any law giving non-whites equality is such that winning them means rejecting – and maybe even
overturning – all civil rights laws. This
illustrative post from Laurence Auster
is extreme right but undoubtedly represents the deep-felt opinion of many, if not most, rural white Americans (more than even Auster realizes). Opinion polls from the middle 1960s suggest that white American citizens, if required to vote on the Civil Rights Act of 1964, would have opposed it by
six- or seven-to-one. Outside academic and political elites, white Americans probably opposed the Civil Rights Act by
thirty- or forty-to-one!
Growing inequality and uniquely high incarceration rates place the Democratic policy of winning at all costs in a bad light. At presidential level, it failed even at its goal, although elsewhere it succeeded until generational turnover in the middle to late 1990s.
If the Democratic Party had maintained its concern with a pure ideology so hostile to essential voting blocs, it would have faced decades in the presidential wilderness and erosion of its legislative base at a much earlier date. Moreover, a Republican Party that achieved hegemony outside the Northeast and Hawaii would no doubt repeal civil rights gains from as far back as the Fourteenth and Fifteenth Amendments if it could.