(L-R) Democratic presidential candidates U.S. Sen. Bernie Sanders (I-VT), Hillary Clinton and Martin O'Malley take part in a presidential debate sponsored by CNN and Facebook on October 13, 2015 in Las Vegas, Nevada.Joe Raedle/Getty Images

LAS VEGAS—Appropriately enough, Democrats placed a big bet during their first presidential debate here this week.

Across almost all domestic economic and social issues, the five contenders, including fortified front-runner Hillary Clinton, offered aggressively liberal positions. The cumulative effect was to place the field measurably to the left of President Obama, who had steered the party in a much more consistently progressive direction than Bill Clinton during his two terms.

The Democrats’ wager is that a combination of changing attitudes and shifting demographics will allow the party’s eventual nominee to sell that ambitious, unswervingly liberal agenda while the country remains closely divided between the parties—and much of the white middle-class remains unconvinced that government activism can improve their lives.

The big exception was foreign policy, where Hillary Clinton frequently presented a more muscular prescription than her rivals or President Obama. But on economic issues the leftward drift was unmistakable. While Clinton consistently stopped short of matching the vanguard proposals of chief rival Sen. Bernie Sanders, even she reprised little of her husband’s trademark call for balancing government activism with reform and fiscal restraint.

“The center of gravity in the Democratic Party has definitely shifted,” insisted Adam Green, co-founder of the Progressive Change Campaign Committee, a liberal group that champions economic populism. “It wasn’t a debate about the direction we go. It was how do we get there and how big do we go.”

The debate seemed likely to reinforce Clinton, who was poised, prepared and professional. Clinton was fluent on issues and unflappable in demeanor, though, until her skilled closing statement, she struggled to strike many inspirational notes.

Sanders was a vivid presence with his full-throated calls for single-payer health care, breaking up big banks, and taxing the rich. But his unflinching presentation was better suited for reinforcing his appeal to white progressives than expanding his reach beyond them, which he must do to seriously challenge Clinton. Among the second-tier candidates, Martin O’Malley showed spark, but still faces a long climb to relevance.

More revealing than the differences among the candidates was their shared convergence around an agenda that cheered liberals. That marked another milestone in a process that has consistently carried the party away from Bill Clinton-style centrism since he left office in 2001.

That change is rooted in the Democratic coalition’s shifting composition. Clinton won his two elections at a time when Democrats could not triumph without running competitively among conservative-leaning voters, particularly older, rural and blue-collar whites. Clinton courted those voters with an agenda that combined government activism with calls for fiscal discipline, personal responsibility, and cultural centrism. That carefully balanced formula allowed him to restore the Democrats’ national competitiveness after Republicans had dominated presidential elections for a quarter-century.

But since 2000, older, rural and blue-collar whites have continued their migration into the Republican Party. Obama still captured the White House twice by replacing them with more consistently liberal groups that are all growing in the electorate: people of color, millennials, and college-educated, single and secular whites, especially women. These dynamics have reshaped the Democratic coalition. While voters who identified themselves as liberals provided only one-third of Clinton’s votes in 1992, they generated 43 percent of Obama’s in 2012. Blue-collar whites provided about one-half of Clinton’s votes in 1992, but just one-fourth of Obama’s in 2012.

On issues from gay marriage to climate, Obama has started recasting the Democratic agenda around this new coalition’s priorities. In the debate, Clinton, Sanders and O’Malley all pushed beyond him with a message of economic populism, activist government and cultural liberalism. Revealingly, the one notable disagreement on social issues came when Clinton attacked Sanders from the left on gun control—an issue that Democrats have mostly feared to touch since 2000.

On economic matters, Sanders planted the flag on the left sideline on issues from single payer health care to expanding Social Security benefits. Clinton almost never matched Sanders, but offered alternatives that moved more carefully in the same direction. In the primary context, that positioned her, sometimes uncomfortably, as the practical champion of the possible to his soaring idealist. (The exchange that best encapsulated the entire debate came when he said the U.S. “should look to” high-tax high-service European countries such as Denmark and Clinton fired back: “We are not Denmark.”)

But if Clinton becomes the nominee her agenda still places her notably to the left of Obama (much less her husband) on most domestic issues. Democrats have reason for confidence they now represent the majority opinion on most cultural questions, like gay marriage. But doubts about activist government remain widespread, particularly among the white middle-class. In polls, most whites consistently say they have not personally benefited from either health care reform nor Obama’s economic agenda.

Even against a Republican Party careening rightward in its nomination fight, Democrats won’t truly know if the gamble they placed in Las Vegas this week has paid out until the party’s eventual nominee tries to redeem it in the decisive swing states during the general election next fall.

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