The future belongs to the young. And that has Hillary Clinton worried.

Millennials, one of the key demographic groups that carried President Barack Obama to victory over Mitt Romney four years ago, appear unwilling to back Obama's former secretary of state.

Journalism professor and blogger Jeff Jarvis, a Clinton supporter, has described this November's Election Day as a "What did you do in the war, Daddy?" moment. Twenty-somethings, however, don't seem to be concerned that their children one day might ask them what they did to stop Donald Trump from becoming president.

Polls show that a large majority of young voters are repelled by Trump. They view the Republican nominee as a racist authoritarian who incites violence and baldly lies about everything. They don't want him to be president.

But that doesn't mean these typically left-leaning voters are willing to vote for Clinton, who they also don't trust. Instead of the Democratic nominee, they are turning to third-party candidates.

Trump doesn't have this problem. Sure, there are some vocal "Never Trump" conservatives, and there's a group called Republicans for Clinton. But polls indicate that the vast majority of registered Republicans are willing to vote for Trump, even if they're unenthusiastic about him or have serious concerns about him.

Here's what a new poll from Quinnipiac says: In a four-way race, Libertarian candidate Gary Johnson and the Green Party's Jill Stein are pulling a combined 44 percent support from voters between 18 and 34 years old. And almost all of it is coming from Clinton's slice of the pie. She was polling at about 60 percent among young voters a month ago; now she's down in the 30s, Vox notes.

Why has this happened? Many reasons.

In the past month, The Associated Press declared that the intersection of Clinton Foundation donations and Clinton's actions as secretary of state raised "troubling questions," a report that other news outlets have exposed as deeply flawed. Plus, there's the continued drip-drip-drip of the email-server scandal. Then came the pneumonia diagnosis that Clinton unwisely kept under wraps until she wobbled at a 9/11 memorial. And finally, Trump and his surrogates have been hammering home the lie that Clinton started the "birther" movement even though they know it isn't true.

The result: Seventy-seven percent of young voters, a heavily Democratic/liberal cohort, do not think Clinton is honest, the Quinnipiac poll indicates. That is an astonishing number. These same potential voters overwhelmingly believe Clinton is more qualified to be president than Trump and that Trump is not "level-headed." Such conflicting beliefs have pushed these young voters to reject both major-party nominees.

This leaves Clinton in a tight spot. She has very little opportunity to pick up the support of Republicans who don't like Trump. The internet has made it easier than ever before for partisans to get away with lies, because people are increasingly walling themselves off from news sources they believe don't fit their worldview. (According to a recent survey, for example, nearly 40 percent of Americans incorrectly believe the Clinton Foundation handles the Clintons' personal finances.) Republicans hate Clinton. They've spent 25 years hating Clinton. They will not be voting for her.

That means she must get her Democratic base to rally around her, like Trump appears to be doing with core GOP voters. The problem is that young voters are an important part of the Democratic base, and Clinton never really had them in the first place. They were Bernie Sanders voters in the Democratic primaries.

Over the weekend, Sanders, recognizing that his former rival is in trouble, appealed to his backers to get behind Clinton. "This is not the time for a protest vote, in terms of a presidential campaign," the Vermont senator wrote on Facebook. "I ran [for the House of Representatives and the Senate] as a third-party candidate. I'm the longest-serving independent in the history of the United States Congress. I know more about third-party politics than anyone else in the Congress. And if people want to run as third-party candidates, God bless them! Run for Congress. Run for governor. Run for state legislature. When we're talking about president of the United States, in my own personal view, this is not time for a protest vote. This is time to elect Hillary Clinton and then work after the election to mobilize millions of people to make sure she can be the most progressive president she can be."

President Obama is making similar appeals to African-American voters, another key Democratic group whose support for Clinton appears to be wavering.

At the same time, as panic rises that Donald Trump really could be elected president, the Libertarian Party's vice-presidential candidate, former Massachusetts Gov. William Weld, is feeling pressure from Washington insiders. Famed Watergate reporter and Clinton biographer Carl Bernstein says Weld, a lifelong Republican who has made clear he "despises" Trump, is considering abandoning the Libertarian ticket and backing Clinton.

Bill Weld could be a hero--instead of a Nader--if he renounces his own Libertarian candidacy and endorses/campaigns for HRC. Stay tuned. — Carl Bernstein (@carlbernstein) September 17, 2016

Johnson and Libertarian Party officials have denied that Weld is thinking about such a move.

So Trump is on the march and Clinton is on the defensive. Recent polls now show the two candidates are about even, that the election will come down to who wins the get-out-the-vote effort in a handful of "battleground" states.

What did you do in the war, Daddy? It appears that, in the years ahead, today's young, progressive voters will be telling their children they helped elect Hillary Clinton -- or they will be guiltily deflecting the question by offering Junior an unexpected ice-cream cone.

-- Douglas Perry