Philip Bump: “For years, Democrats were much more likely to call themselves ‘moderate’ than ‘liberal,’ according to data from Gallup. In 2000, 44 percent of Democrats described themselves as moderate, compared to 31 percent of Republicans who identified themselves that way. Twice as many Republicans called themselves “conservative” — as did a quarter of Democrats. “Liberal” was the least common way Democrats referred to themselves. That has changed — fast.”
Now, Democrats are far more likely to call themselves liberal than moderate. Compared to 2007, the year before the last contested Democratic primary, Democrats are seven percentage points more likely to identify as liberal and three points less likely to identify as moderate. Compared to 2003, when Dean hoped to ride a progressive wave to the White House, Democrats are 13 points more liberal — and eight points less conservative.
So. It may not be so much that Sanders is driving liberals to the polls or pulling his party in a more progressive direction as it is that Sanders is doing unexpectedly well because his party has already moved to the left. After all, Sanders only won the “very liberal” vote in Iowa by 19 points — far less than the percentages by which he won young people, for example. Among the “somewhat” liberal voters, Clinton won by six.