This poll number should be a warning sign for Hillary Clinton

Democratic presidential frontrunner Hillary Clinton is broadly popular with Democrats, according to a new poll from the Pew Research Center. But a deeper look at those numbers suggests there could be some cracks in the foundation.

One of the potential hiccups with Clinton’s second round of campaigning comes with an issue from her first — a perceived problem with young voters.

The precedent for this perception: In 2008, Clinton was beat handily by President Barack Obama among youth voters in the Democratic primary. He tripled her share of the youth vote in Iowa — something that prompted a top Clinton adviser to famously say that Clinton voters “look like caucus-goers and his people look like they are 18.”

The new Pew poll suggests she could have the same problem with the youth vote in 2016 — or, at least, that she’ll need to do some serious work to turn out young voters at levels that would be beneficial.

The poll found that Clinton is viewed less favorably among younger Democratic voters. Overall, 72 percent of younger voters who either lean toward or identify as Democrats view her favorably. That’s a 15-point drop from the same period in 2008, and it’s 5 points below the overall percentage of Democrats who view Clinton favorably (77 percent).

But whereas what Pew terms as “older millennials” — those old enough to vote in the 2007-08 Democratic primaries — generally view Clinton more favorably (79 percent), it’s clear she has a bit of a perception problem with “younger millennials.”

Among those “younger millennials,” who were not old enough to vote in 2007-08, only 65 percent view her favorably. That’s a concerning 17-point drop from last August, when 82 percent of that crowd viewed her favorably. And the same group of 18- to 25-year-olds viewed her favorably at an 87 percent clip around this point in 2007.

Here’s a breakdown from Pew:

That said, other polls have shown Clinton maintaining a clear edge over both Democratic and Republican rivals in the early stages of the 2016 campaign. A Fusion poll conducted earlier this year found that 57 percent of young Democrats preferred her as the nominee, while most said they would lean toward the Democratic candidate.

Other polls have displayed Clinton building a decent base among young Democrats and women. Here’s how she fared against potential Republican rivals among voters aged 18-39, according to a Quinnipiac University poll in April:

• Clinton 63, former Florida Gov. Jeb Bush 30 (Clinton leads 53-41 overall among registered voters)
• Clinton 67, Texas Sen. Ted Cruz 26 (56-39 overall)
• Clinton 64, Wisconsin Gov. Scott Walker 29 (54-40 overall)
• Clinton 66, Florida Sen. Marco Rubio 26 (54-39 overall)

Brett LoGiurato is the senior national political correspondent at Fusion, where he covers all things 2016. He’ll give you everything you need to know about politics, with a healthy side of puns.