WASHINGTON -- Hillary Clinton had a great night on Saturday. The Democratic Party had a terrible one.

Clinton trounced Sen. Bernie Sanders by nearly 3-to-1 in the South Carolina primary, winning every single county in the state. The thumping followed a convincing Clinton victory in the Nevada caucuses less than a week earlier, and sets the stage for a strong showing for Clinton on Super Tuesday, when 11 states are in play.

For the Democratic Party establishment, these wins are being interpreted as a sign that the universe is back in order, after a 74-year-old democratic socialist from Vermont had seemingly knocked everything out of orbit. Party leaders long ago picked Clinton as their standard-bearer for 2016 and worked to clear the field of potential primary challengers. When Sanders began closing on Clinton in national polls and clobbered her in New Hampshire, the establishment bet was starting to look shaky. Had they lost touch with the core concerns of the party's base? After South Carolina, Sanders' chances to secure an upset nomination are dwindling.

Exit polling showed that Clinton won every demographic tracked except voters under 30. Even here, she was far more competitive with Sanders than in prior contests, losing just 54 percent to 46 percent. She even won a higher share of the black vote than Barack Obama did in 2008.

But Democratic Party elites shouldn't be high-fiving each other. They should be very, very worried.

In primary after primary this cycle, Democratic voters just aren't showing up. Only 367,491 people cast a ballot for either Clinton or Sanders on Saturday. That's down 16 percent from the 436,219 people who came out in 2008 for Clinton and Obama. Factor in the 93,522 people who voted for John Edwards back in the day, and you can see the scope of the problem. Democrats in 2016 are only getting about two-thirds of the primary votes that they received eight years ago.

Republican turnout in the South Carolina primary, by contrast, was up more than 70 percent from 2008.

South Carolina's turnout numbers are not an anomaly. They're consistent with other primaries to date. Republicans are psyched. Democrats are demoralized.

Presidential elections increasingly hinge on each party's ability to turn out the faithful. There simply are not many truly independent voters who cast their ballots for different parties in different cycles. A big chunk of voters who identify as independents do so not because they cherish a moderate middle ground between two parties, but because they see their own party as insufficiently committed to its ideological principles. In this era, lousy primary turnout spells big trouble for the general election.

The poor Democratic turnout figures are not an indictment of Clinton alone. Maybe the DNC's decision to bury the party's debates on weekends and holidays helped Republicans generate more early enthusiasm with primetime coverage. And part of Sanders' pitch, of course, is his insistence that progressive energy will bring out high numbers of enthusiastic voters that an old party insider just can't compete with. It's a good pitch. But so far, it isn't happening.

It's always hard to motivate voters for four more years of the same old thing after getting eight years of it -- especially when many of those years were mired in an awful recession, followed by a weak economic recovery. Opposition parties typically have a better hand after eight years. That's why 12-year runs in the presidency by a single party don't happen very often.

If Republicans nominate Donald Trump for president -- and barring a cataclysm or a coup, they will -- there will be plenty of energized Democrats who turn out in the general election for no other reason than to cast a ballot against a billionaire who has predicated his campaign on raw bigotry.

That will help even the energy some. But the flip side of the coin is that lots of angry white people will show up to vote for Trump. We know because they're already doing so in the primaries. And a lot of Republican partisans who prefer other candidates still care more about turning the page on the Obama era than they do about Trump's flirtations with fascism (and even, at times, liberal critiques of GOP orthodoxy).

Trump's overtly racist campaign makes it hard to see how he wins Western swing states like Nevada or New Mexico that have high numbers of Latino voters. But his economic pitch to the white working class holds obvious appeal in traditional Democratic strongholds in the upper Midwest -- communities that have been ravaged by the past three decades of U.S. economic policy. Even if Trump lost every other swing state in the country, turning the Rust Belt red would be enough for him to win the Electoral College.

That's a difficult maneuver. But it's time to start worrying about President Trump.

Zach Carter is a co-host of the HuffPost Politics podcast "So, That Happened." Subscribe here or listen to the latest episode below: