Let’s start with ideology. Fifty-two percent of registered voters expressed positive views about capitalism, compared with 18% voicing negative views. Regarding socialism, only 19% were positive while 53% were negative, including 41% who were “very negative.” These numbers haven’t budged over the past 15 months. The Republican attack on socialism, a steady drumbeat since last year’s State of the Union address, would throw Sen. Sanders on the defensive…

Unless a Sanders candidacy could somehow reconfigure the political map, he would need to retake at least Pennsylvania and Michigan to have a serious shot at 270 electoral college votes. But the less-educated white voters who dominate these states’ electorates are hostile to socialism, even more so than whites with college degrees. Only 12% of white voters without college degrees are favorable toward socialism, while 63% disfavor it—and 54% view socialism in a very negative light. Whatever the case in Vermont, socialism is not a winner in the Midwest.

Mr. Sanders claims his uncompromising message gives him a unique opportunity to translate popular passion into votes. If so, the NBC/WSJ poll results don’t show it. Only 13% of voters report being “enthusiastic” about his candidacy, compared with 43% who are “very uncomfortable.” (The comparable numbers for Joe Biden are 14% and 35%.) Among swing voters, 31% are very uncomfortable with Mr. Sanders, compared with only 19% feeling the same about Mr. Biden.