Scott Olson via Getty Images Democrats are showing up in large numbers in the states that end up voting for Bernie Sanders. But turnout hasn't been as high in states that ultimately voted for Hillary Clinton.

WASHINGTON -- So far in the Democratic primary, there's only one set of circumstances in which the party is producing strong voter turnout: When Bernie Sanders wins a state, tons of voters are showing up.

In Colorado, Kansas and Maine, Democrats have actually surpassed the turnout of the 2008 primary contests, while the caucuses in Minnesota and Nebraska only narrowly missed. Sanders won all five states. That's no small feat. Democrats were energized in 2008, eager to turn the page on the Bush years, and excited by two candidates whose election would have represented a breakthrough for millions of people.

But much of this primary season has been a different story. In every state that Hillary Clinton has won -- which is most states -- the party is seeing a significant decline in voter turnout from the 2008 election. Half as many Texas Democrats came out to vote this year than in 2008. In South Carolina, turnout was down by a third. Virginia? Down by one-fifth.

A lot of these states don't really matter -- Democrats aren't going to win Mississippi or Alabama, no matter how many people show up at the primary, and they aren't going to lose Vermont no matter how many people are feeling the Bern.

But low turnout should be at least somewhat worrying to party leaders, since Clinton will almost certainly be the eventual Democratic nominee. There aren't many independent voters anymore. People like to tell pollsters they're independent, but the voting patterns of these people are typically heavily partisan. The Democratic Party has a major demographic edge over Republicans -- if it can get the Obama coalition of black, Latino and Asian-American voters to show up at the polls. When they do, as in 2012, they win. When they don't, as in 2014, they lose.

The good news for Clinton is that low turnout at the primary stage doesn't mean a party will lose in the general election. As Nate Silver has noted, the party that secured the most primary votes has lost seven elections since 1972. But it's still a meaningful way to gauge the excitement among a party's base. Ask anyone at the Democratic National Committee whether they'd like to see good turnout numbers in the primary, and they'll tell you that, yes, of course they would.

Clinton has also been a national political figure for almost a quarter-century, and it's hard to get voters enthused about the status quo in a year in which Washington politics isn't very popular. Many Democrats cast their first vote for a woman president in 2008. The second one just isn't historic.

Still, a full 79 percent of Democrats say they would be satisfied with Clinton as the party's nominee. By contrast, only 49 percent of Republicans say the same of Donald Trump, who is likely to be the GOP standard-bearer in the fall. And if Trump becomes the nominee, his flagrantly racist campaign rhetoric will surely motivate large numbers of Democrats to come out to the polls if for no other reason than to vote against him.

Trump's hostility to minorities makes it hard to see him winning swing states like Nevada and Colorado that have large numbers of Latino voters. But he could win the presidency if he can flip the Rust Belt for Republicans. And Trump did, in fact, ride criticism of U.S. trade policy to a victory in Michigan on Tuesday night. Michigan, meanwhile, is one state in which a Sanders victory has not translated into great numbers for Democrats. While both Clinton and Sanders easily beat the state's 2008 turnout numbers for Clinton and Obama, Michigan's primary wasn't hotly contested that year -- the state was being punished by the DNC for violating its primary scheduling rules. And on Tuesday, Republican turnout in Michigan eclipsed the Democratic total by 10 percent.

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