Pete peeled off many college-educated voters who were deciding between him and Warren, and health care was a main reason why. The writer contradicts himself here but he gets the dynamic right:
If you make a timeline in Iowa and New Hampshire of Warrens rise and fall, you see her taking first place in both states in October after Bernie Sanders heart attack. In Iowa, her poll numbers begin to decline about ten days into November; in New Hampshire, later in the month. Most commentators attributed her decline to the publication of her Medicare for All plan, but I find that implausible. She was just spelling out a position she already had taken. Maybe the awkwardness was a factor, but Id say two other things were important.
First, Sanders regained his footing after his heart attack, and his supporters who had gone to Warren switched back. Secondly, Buttigieg, who had once been an enthusiastic supporter of Medicare for All, but sensed an opportunity on Warrens right, began attacking her stand and peeling off her votes, and in general repositioning himself toward the center. When I was in New Hampshire last fall interviewing people at Warrens rallies, what I often found, particularly among the Dartmouth/Hanover and upper-middle-class voters, was their deliberating between Warren and Buttigieg not Warren and Sanders. Hanover, as it turned out, went strongly for Buttigieg in the primary.
https://talkingpointsmemo.com/edblog/requiem-for-elizabeth-warrens-presidential-campaign