(CNN) Vermont Sen. Bernie Sanders' presidential campaign is in trouble.

While much of the attention in post-debate polling has focused on the drop of former Vice President Joe Biden, Sanders' polling looks far worse. Sanders' Iowa and national polls are quite weak for someone with near universal name recognition.

Sanders was at just 14% in CNN's latest national poll . That's down from 18% in our last poll. As important, Sanders is now running behind California Sen. Kamala Harris (17%) and Massachusetts Sen. Elizabeth Warren (15%). These are candidates who have lower name recognition than he does.

It's not just the CNN poll, either. Sanders doesn't look much better in Quinnipiac's latest poll, which puts him at 13%. A poll released Wednesday morning by ABC News and The Washington Post did have somewhat better news for him, putting him at 19%, second behind Biden, among Democrats and Democratic-leaning independents. Still, an average of the three polls out this week puts him at 15%.

History has not been kind to primary runner-ups of previous primaries polling this low of a position. I went back and looked at where 13 previous runner-ups since 1972 have been polling at this point in the primary. All six who went on to win the nomination were polling above Sanders' 15%.

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