Tuesday was a very good day for Hillary Clinton. She swept primary challenger Sen. Bernie Sanders (I-Vt.) in five states, effectively ending his chances of securing the Democratic presidential nomination. But buried within the clear victory was a troubling trend for the party front-runner: She is doing a terrible job turning out voters, particularly in the states that will matter most in a November matchup against Donald Trump.

More people voted for Trump than for Clinton in two states Tuesday night -- Missouri and Ohio. In Florida, Clinton edged Trump by a nose -- less than 2 percent. Clinton had only one other candidate splitting the Democratic vote in a contested election, while Trump was embroiled in a four-way contest that factionalized Republican voters. In Ohio, Trump bested Clinton by about 50,000 votes despite coming in second in the GOP contest to John Kasich, the state's current governor. In Missouri, both Trump and Sen. Ted Cruz (R-Texas) bested Clinton's vote total by nearly 20 percent.

Enthusiasm for Clinton appears to have plummeted from the levels she enjoyed in 2008, when she defeated Barack Obama in both the Florida and Ohio primaries. Clinton had 44 percent fewer supporters in Ohio this time around than she did eight years ago. Combine Clinton and Sanders' Ohio numbers from Tuesday night and they still do not eclipse Clinton's showing in the state from 2008.

Since Florida, Missouri and Ohio are traditionally swing states in the general election, these results should be causing some worry at the Democratic National Committee -- Ohio most of all. Democrats are simply performing poorly in the Rust Belt this year. And the only way Democrats will blow a November matchup against Trump is by getting beaten in the upper Midwest.

Trump has been running a flagrantly racist campaign. Given the vitriol he has directed at Latinos, it's hard to imagine him winning swing states like New Mexico or Colorado (although as Tuesday's results show, Florida may not be out of reach). But Trump doesn't need those states to take the presidency. All he has to do is turn the Rust Belt red.

Obama cruised to re-election four years ago with 332 total electoral votes, 62 more than the 270 needed to win. If Trump were to turn Ohio, Pennsylvania, Michigan and Wisconsin, however, he'd have enough electoral votes to best whoever wins the Democratic nomination -- even if he lost every other swing state except Missouri.

That's a tall order, of course, but it's not impossible. Wisconsin, Ohio and Michigan all have a Republican governor, as did Pennsylvania until 2015. All four of those states are significantly whiter than the national average.

And so far, Trump's been landing body blows in the Rust Belt on the Republican side. He crushed in Michigan and Illinois, won Missouri and lost to Kasich in the state where Kasich is currently the governor. More Republicans voted in the Michigan primary than did Democrats.

Primary turnout levels don't offer a surefire forecast of general election results. One party turning out more voters during the primaries often does not translate into a victory in November. But there isn't much data for this kind of situation one way or the other. Since 1972, only three elections have featured contested primaries in both parties, and in two of them, a sitting vice president quickly sewed up his party's nomination, eliminating urgency in later states.

If Trump becomes the Republican nominee, that could be all the motivation Democrats need to show up at the polls. And a full 79 percent of Democrats say they would be satisfied with Clinton as the party's nominee in November, while only 49 percent of Republicans say the same of Trump.

But that last figure is certain to increase once Trump formally secures the GOP nomination. And in the meantime, Trump's fascist-tinged demagoguery is winning him plenty of enthusiasm.

It's going to be a long eight months.

Editor's note: Donald Trump is a serial liar, rampant xenophobe, racist, misogynist, birther and bully who has repeatedly pledged to ban all Muslims -- 1.6 billion members of an entire religion -- from entering the U.S. Zach Carter is a co-host of the HuffPost Politics podcast "So, That Happened." Subscribe here or listen to the latest episode below: