New polls released this week suggests Hillary Clinton has a growing problem with millennial voters and that's a major concern for the Democratic presidential nominee.

Both national polls and surveys in swing states show Clinton has seen a slide with voters younger than 35, particularly when Libertarian candidate Gary Johnson and Green Party candidate Jill Stein are factored in.

A national Quinnipiac poll showed Clinton capturing 31 percent of the vote among voters 18-to-34 years of age and a slim 5-point lead over Trump. In August Clinton had 48 percent of that vote and a 24-point lead over Trump.

A Fox News poll of the national electorate showed Clinton winning 37 percent of the youth vote and leading Donald Trump by 9 points. In August, the poll showed her support at 39 percent and leading Trump by 8 points.

In Ohio, a CBS/YouGov poll showed Clinton doing better with voters under 30, winning 51 percent of them and holding 32-point lead on Trump. But that number was down from August when Clinton won 57 percent of that vote and a held a 38-point lead.

A Detroit Free Press poll in Michigan showed a big dip among voters under 35. In the new poll she has 31 percent of that vote and a 7-point lead over Trump. In August she had 44 percent of that vote and a 24-point lead.

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The lower numbers are a big problem for Clinton because Democrats need a lot of votes from the younger part of the electorate to offset losses they normally get with older voters. Consider 2012 when Millennials gave President Barack Obama his biggest numbers by far. He captured 60 percent of the under-30 vote in the national electorate, compared to just 37 percent that went for GOP nominee Mitt Romney.

Obama did even better with that age group in Michigan and Ohio with 63% of the under-30 vote.

It's an issue Obama himself addressed in his campaign appearance in Philadelphia last Tuesday. In trying to rally the coalition that elected him twice to get enthusiastic about backing Clinton, the president took a moment to address young voters:

"And the young people who are here, who all you've been seeing is just the nonsense that's been on TV, you maybe don't remember all the work that she has had to do and all the things she has had to overcome and all the good that has happened because of her efforts. But you need to remember. ... She's in the arena and you can't leave her in there by herself, you've to get in there with her. You can't stay home because, you know, she's been around for a long time. Well you know what? This is not reality TV. Democracy is not a spectator sport. You don't tweet in your vote."