Too much is made of the Eagleton mistake and of the move to the center: McGovern was understood by all to be the most Left-wing candidate any major party had ever nominated. Everyone with a semi-progressive thought in their brain voted for him. He was the candidate of hippies, marijuana smokers, and the whole counterculture. Nixon was square as they come, yet he cleverly portrayed himself as the New Nixon with moderate suburban views who was friendly to women’s rights and the environment. He was able to do this while still appealing to truck drivers and industrial workers as a patriot who was on their side of the social culture wars. Finally he was actually extricating us from Vietnam. As the draft notices dwindled to zero, the appeal of an anti-war candidate dropped as well. There may have been a plurality of assorted Maoist, Weather Underground, and Radicals in a few college communities and communes. But in large parts of the country, there was no silent majority for McGovern. The country had turned the page on the 60’s. It had permanently changed in many ways, but it did not want any more changes in that direction. McGovern actually had more votes than real supporters. There were large numbers of people then who voted Democratic as a habit or were loyal to party machines, but who didn’t agree with anything McGovern stood for.
Please spend some time travelling in the farming and industrial MidWest, or the rural South, or in the Plains or the West outside the coasts, places Trump won by over 10 points. You’ll find there are no untapped pools of Progressive voters out there. Go far enough Left and many of the Democratic moderates, the ones who gave the Democrats a House majority, will opt for a centrist third-party candidate. In a dozen states, the Democratic Party candidate will come in an embarrassing third place. After reading your piece I realize the delusion never died. Every generation the Democrats need to nominate one of those Progressives to relearn the lesson of McGovern’s defeat.