Paul Krugman clearly supports Clintion in the primary, and for sensible reasons. But his attacks on Sanders supporters are, frankly, bonkers. While I'm sure there are people who support Sanders for the reasons he mentions, generalizing from them is like the people who generalize from a small number of Clinton supporters who only support her because she is a woman. It's, for lack of a better word, stupid.
I find the attacks on both of the Democratic candidates (remaining) to be pretty small minded, petty and, yes, stupid. While it isn't surprising from many people I would think Krugman would be more thoughtful about it, but he really seems very reactionary and defensive.
I read the Vox article he quotes from and my takeaway was that this election has messed with the historical based prediction models and you can't effectively extrapolate what will happen. If a more conventional Republican were to win, then maybe you can go back to those. But that is looking less likely as time passes, and if the GOP nominee is Trump or Cruz or even Rubio then you are likely looking at a general that will not shape up as the historical models would predict.
Also, that Nixon - McGovern as a basis for comparison is just weird. Yes, McGovern was a radical liberal, but Nixon was to left of much of his party's base and in many ways more liberal than most "conventional" Democrats today, including Obama and Clinton. He was a Keynesian for God's sakes! If you really wanted to try and parallel that election then Cruz is the McGovern equivalent and Hillary would be Nixon (she is to the right of most of her party base, Cruz is a radical conservative). Trump is who the hell knows what, and Sanders is, in reality, only a bit more liberal than Clinton. Mostly he is just not apologetic about his liberalism, and that matters to lots of Democrats who are tired of politicians who they vote for not representing them. Not defending their views.
In terms of what can be accomplished, neither Clinton nor Sanders will be able to do much as president thanks to the US House (gerrymandering has pretty much guaranteed a GOP majority until 2022). It may be that Clinton will be better at getting things done in spite of that. It could also be that Sanders would be able to shift the Overton window such that better results become possible [in the future].
Who the fuck knows?