Democratic debate shows a party moving leftward

For nearly all of the 2016 Democratic presidential candidates — former Sen. Jim Webb being the notable exception — Tuesday night’s CNN debate was a race to the left.

That was especially true for the two leading candidates, front-runner Hillary Clinton and runner-up Sen. Bernie Sanders of Vermont. Sanders, a democratic socialist, has staked his campaign on a pledge to combat wealth inequality and to import elements of Nordic social democracy to the United States; Clinton has hewed closer to the center, but nonetheless said Tuesday that she supports efforts to check “the excesses of capitalism."

Overall, the party on display during the debate appeared to be a far cry from the one led by welfare reformer and financial deregulator President Bill Clinton in the early 1990s. The Progressive Change Campaign Committee (PCCC), which identifies itself as part of an intra-party liberal vanguard led by Sen. Elizabeth Warren of Massachusetts, said in a Tuesday night statement that the debate “shows that bold progressive ideas are baked into the DNA of this election."

“This debate felt like a real primary — and the Elizabeth Warren wing of American politics has clearly shifted the center of gravity in the Democratic Party,” the PCCC said. “This was the first presidential debate in history where debt-free college, expanding Social Security benefits, breaking up Too Big To Fail banks and criminal prosecution of Wall Street bankers were big issues."

A wealth of political science research shows that the debate’s liberal tilt was not an election-year blip. The Democratic Party is making a substantive shift toward the left. The reasons have less to do with Elizabeth Warren than with tectonic shifts in American income inequality.

There is a longstanding consensus among political scientists that America’s two major parties are becoming more polarized, but that polarization has not been symmetrical. A June 2014 survey from Pew Research Center charted the last two decades of polarization and found that the median Republican voter began hurtling away from the center and toward the right circa 2004. Democrats moved left between 1994 and 1999, but then kept relatively static until 2011.

But then the party lurched in a more progressive direction again between 2011 and 2014, such that Pew found the share of Democrats “who are consistently liberal has quadrupled … over the past 20 years."

More recent investigations support this conclusion. A Gallup poll from June of this year found that the share of Democrats who “identify as social liberal and economic moderate/liberal” — as opposed to those who describe themselves as economic conservatives — has risen from 30 percent to 47 percent since 2001.

One of the biggest factors driving this ideological shift may be the widening chasm between the rich and everyone else. In late August researchers at Princeton, Georgetown and the University of Oregon issued a research paper finding a causal link between growing income inequality and increasingly assertive Democratic liberalism on the state level. The researchers do not speculate at length about why the causal link exists, but suggest that Democrats may in part be influenced by growing "demands for redistribution."

That comports with worldwide trends in political economy. As global inequality has continued to rise, insurgent left-wing political factions have to come to overtake the center-left in a handful of other Western states. The most recent example is the surprise victory of perennial back-bencher Jeremy Corbyn in the 2015 leadership race to head the United Kingdom’s Labour Party.

Corbyn’s rise has been widely regarded as a death knell for Tony Blair’s center-left New Labour movement. As the Democratic Party in the United States apparently heads toward a similar ideological transformation, the extinction of its own mid-'90s centrist wing may also be at hand.