It's the nature of party primaries that candidates move toward the extremes. After all, in an election that only includes Democrats or only includes Republicans, candidates are more likely to embrace issues that appeal to as many members of that party as possible. So the Republican victor in Iowa, a state with a lot of conservative Republicans, was Ted Cruz.
The Democrats have been less enthusiastic about embracing their party's extremes. Al Gore brushed off Bill Bradley in 2000. The party flirted with Howard Dean in 2004, but eventually backed John Kerry, worried about winning the general election. In 2008, Barack Obama and Hillary Clinton were about evenly matched on ideology and the far-left candidate, Dennis Kucinich, wasn't viable, so Obama won that year.
But in 2016, Bernie Sanders nearly won Iowa. Sanders is unabashedly liberal. He's a self-described democratic socialist, and fought Clinton to a draw. Nor is he letting up. He spent a good part of Wednesday tweeting disparagement of the authenticity of his opponent's bona fides.
He called Clinton out (often not by name) on raising money from Wall Street, on the Keystone XL pipeline and, of course, on her vote in favor of the war in Iraq. Clinton has tried to move left to counter Sanders's strength on a lot of these issues, with mixed success. The turf on which the two are fighting now is much further from the center than it was in 2008.
The second-to-last poll from Selzer & Co., the respected Iowa pollster, found that nearly half of Iowa Democrats saw themselves more as socialist than capitalist. Which by itself suggested that Sanders would do better in the state that you might suspect. When the first entrance polls came in, it was clear that the electorate in 2016 was much more liberal than it had been eight years ago with the election of Barack Obama.
Is that move to left attributable to the Sanders effect? Not necessarily.
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.
It's worth noting that Sanders's use of "progressive" (like mine, above) emerged as a way of saying "liberal" at a time when "liberal" had a more pejorative connotation. (See also: "socialist.") We're talking about labels here, but it's clear there's some overlap with policies.
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.
Democrats are still much more moderate than Republicans are. In Congress, Republican elected officials, powered by right-looking primaries, have moved to the right faster than Democrats have moved to the left.
If the trend seen in Gallup's polling continues, it's candidates like Bernie Sanders, not like the Hillary Clinton of 2008 who are the future of the party's nominating process.