Hillary Clinton makes big promises to Bernie's millennial fans — but can she keep them?

After defeating Bernie Sanders in a brutal Democratic primary fight, presidential nominee Hillary Clinton still had something to prove to the legions of young voters who embraced the Sanders political revolution.

In a "Jobs Plan for Millennials" touted ahead of her major tax policy address Wednesday, Clinton made a direct economic play for Sanders followers.

It plays up Clinton's pledge to "achieve the goal of free community college, free tuition for working families at public four-year colleges, increased support for career and technical training, and a debt free future for all Americans," for example.

Clinton's outreach to millennials, who overwhelmingly supported Sanders in the primaries, promises $20 billion to create job opportunities for the young. She proposes tax credits for businesses that offer apprenticeships. She emphasizes job creation in clean energy and the tech sector.

For her tax-plan rally this week, Team Clinton pointedly chose the backdrop of an Ohio high school — a day after her byline appeared on an op-ed for Teen Vogue.

Both the millennial jobs plan and the tax strategy are being sold as a sharp contrast with the offerings of Republican Donald Trump, whose campaign has made noise about positioning the GOP nominee as an alternative for Sanders loyalists who don't want to default to Team Clinton.

But Clinton herself is borrowing straight from the Sanders playbook as she looks to gin up excitement about her candidacy.

The latest polling strongly suggests that while millennials cleaved to Sanders in the primaries, they're flocking to Clinton in the general election and leaving Trump in the dust.

The Trump campaign, amid yet another top-tier management shake-up, did not respond to a request for comment.

The larger question — barring some seismic change in the leanings of millennial voters, particularly former Sanders backers — then becomes whether they're excited enough about the Clinton plan, or worried enough about the Trump plan, to actually get out and vote.

"While Donald Trump continues to bully and belittle his way through this election, our campaign will remain focused on communicating the truth of Hillary's values to millennials and sharing the many ways her plans will create a stronger future for the generation," said Clinton spokesman Christopher Huntley.

Ross Eisenbrey, vice president of the liberal Economic Policy Institute think tank and a Sanders supporter in the primary, said in an interview that the millennial plan shows Sanders had a true impact on Clinton's platform.

"I think he made a big difference. I think he sharpened her attack on the wealthy and has pushed her to do more on, for example, fighting corporate offshoring of profits," Eisenbrey said, also lauding Clinton's stances on debt-free college and opposing the Trans-Pacific Partnership trade deal.

Eisenbrey went so far as to call Clinton's overall blueprint "the most powerful progressive economic platform that the Democrats have had."

And Joe Dinkin of the Working Families Party — which just endorsed Clinton after having backed Sanders — praised her millennial proposal for "big steps in the right direction" on addressing higher education costs and climate change.

Soothing to Sanders fans? Quite likely, Eisenbrey said.

Likely to make it through Congress? Could be a different story.

"All of it is more ambitious than can be achieved with the House of Representatives [and] the Senate that we have today," he said. "If she wins big enough and flips the Senate and by some miracle flips the House, then there's a chance of achieving all of these things that she's talking about."

That's where turnout will matter: While 69 million millennials and 69 million baby boomers are eligible to vote in November, boomers have a 69% turnout rate to just 46% for millennials.

Clinton and her compatriots have warned against a complacency that could dampen turnout, particularly in light of her healthy lead in national polls — polls which reflect a post-convention bounce, but one of as-yet unclear longevity.

While Clinton is now the preferred pick of millennials in all these polls, some young people motivated specifically by the Sanders "revolution" could actually still stay home — or vote third party — at the moment of truth.

The hassles of casting a ballot might also turn off younger voters, affecting not just the top of the ticket, but down-ballot contests as well.

And although Trump has alienated some of the GOP faithful with his bombast, polls in states like Virginia show that his fans are more likely to actually follow through and vote for him than those who say they support Clinton.

All this is not to say Clinton appears in immediate danger of losing to Trump, who has little time left to regain lost ground — even with groups his predecessors carried comfortably, such as white Republican women.

What it does mean is that if Clinton can't stir enough enthusiasm to vault to a decisive November win and help down-ballot allies do the same, she can make all the Sanders-style promises she wants now — but end up unable to deliver on them as president.

Republicans wary of Trump are increasingly talking about focusing their efforts, financial and otherwise, on winning Congressional races. A hostile Congress would spell trouble for any president — just ask Clinton's husband.

As Darrell West of the Brookings Institution put it, "Mobilizing millennials is key to winning and governing. [Clinton] needs a big turnout not just to become president, but to be able to put her policies into action."

"Democrats are in great shape to retake the Senate, but also need the House in order to implement many of her ideas. Without a strong turnout from young people, it will be hard to get the House back," West added.