Drop into a political gathering almost anywhere in America, and you can usually name the party just by looking: Democrats increasingly reflect the racially mixed demographics of the nation's cities; Republicans remain overwhelmingly white, older and more rural.
That hasn't always been true — a generation ago, the voters supporting the two parties were far more alike.
Now, a new, large-scale study has documented how much the mix of voters who support each of the two parties has changed. The conclusion: The two party coalitions are now more different than at any point in the past generation.
The Democrats have changed the most, as the mix of voters who support them has grown less white, less religious, more college-educated, younger and more liberal over the past decade, according to the study by the nonpartisan Pew Research Center.
Republican voters, by contrast, more closely reflect the demographics of an earlier, mostly white, Christian America. In one regard, the party's voters have actually stepped slightly back in time — Republicans are less likely today than a decade ago to be college graduates, Pew found. That's a striking fact in a country that has steadily grown more college-educated.
"Republicans have not changed as the country has changed," said Carroll Doherty, Pew's director of political research.
The numbers, drawn from 10,000 voter interviews that Pew conducted last year, paint a detailed picture of the coalitions behind each of the two major parties. They underscore an important point about the polarization that so dominates national politics: Although Americans often blame politicians for not compromising, elected officials represent voter bases that each year have less and less in common.
Overall 50% of registered voters identify as Democrats or as independents who lean Democratic, Pew found. By contrast, 42% either identify as Republicans or lean toward them.
A much smaller group identifies as independent and does not lean to either party.
The 50% figure marks an uptick for Democrats. It's the first time since 2009 that half of registered voters in Pew's surveys have identified as or leaned toward the Democrats. The 8-percentage-point margin over the GOP is the largest the Democrats have enjoyed since then and is consistent with other polling data showing the Democrats gaining ground since President Trump's election.
But the share of voters overall who support each party has changed just a little. By contrast, the types of voters behind each party has changed a lot.
The changes among Democrats have shifted the party to the left. A decade ago, the largest group of Democrats, 44%, described their views as "moderate." Today, the largest group, 46%, identifies as "liberal," with 37% calling themselves moderate and 15% conservative.
Republicans have been a mostly conservative party for years and continue to be so, with about two-thirds identifying themselves as conservative, 27% moderate and just 4% liberal.
Democrats have benefited from two of the biggest shifts in recent years — the movement of women and college graduates in their direction.
On the other side, Republicans have gained loyalty among white voters without a college degree. They now hold a bigger advantage among that group — which remains the largest demographic group in the electorate — than at any point in more than two decades. Republicans have also gained in rural areas.
Trump's winning campaign in 2016 took advantage of those trends — driving up turnout among non-college white voters in some key states. But his emergence as the face of the GOP also appears to have accelerated shifts away from the party, endangering its hold on Congress this year.
Trump almost certainly has contributed to the movement of women toward the Democrats, a long-term trend that gained strength in the past two years. More than half of women, 56%, now side with the Democrats, compared with 37% for the Republicans, Pew found.
By contrast, the partisan split has not changed much among men: 48% identify with the Republican Party or lean Republican, while 44% are Democrats or lean Democratic.
The president also seems to have energized the educational divide. Voters with a college degree, who now make up a third of the U.S. electorate, increasingly cast Democratic ballots.
As recently as the George W. Bush administration, most college graduates favored Republicans. Today, the share of college-educated voters who either identify as Democrats or lean to them, 58%, is the highest it's been since Pew began studying the data in 1992.
By contrast, the share of college graduates who either identify as Republicans or lean toward them has fallen to 36%.
Because minority voters of all educational levels heavily side with the Democrats — nonwhites make up nearly 40% of Democratic voters but only 14% of Republican voters — the divide by education level is most noticeable among whites.
White college graduates side with the Democrats 53%-42%. As recently as two years ago, white college graduates were evenly split.
But even as they have lost ground among college graduates — and especially those with post-graduate or professional degrees — Republicans have gained with those who did not get a college degree.
The two trends have dramatically reshaped the party coalitions. When Bill Clinton began his second term as president in 1997, more than half of the voters who sided with the Democrats were whites without a college degree. Today, blue-collar, white voters make up only about one-third of those who identify as or lean toward Democrats.
"That's a big shift over 20 years," Doherty said.
By contrast, non-college-educated whites continue to account for about 6 in 10 of those who identify as or lean toward Republicans.
The parties also divide notably by generation and by religion.
Almost 6 in 10 millennials side with the Democrats, a figure that rises to an eye-popping 7 in 10 among millennial women.
By contrast, those now in their 70s and older side with the GOP. Just over half of that generation either identifies with the GOP or leans toward it, while just over 4 in 10 side with the Democrats.
The generations in between are closely divided. Younger Americans are far more likely than their elders to have no religious affiliation. The religiously unaffiliated now make up about one-third of Democratic voters, but only about one-eighth of Republicans.
By contrast, about two-thirds of Republicans are white Christians, especially white evangelical Protestants. Among Democrats, only about 3 in 10are white Christians, and white evangelical Protestants make up only a small share.
Over the long run, the generational difference could be a big problem for Republicans. For now, however, they benefit from older voters' tendency to turn out more regularly, especially in nonpresidential elections.
One of the big questions for U.S. politics, said Doherty, "is when this generational tide starts to really impact elections."
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