Beyoncé chats with former president Bill Clinton backstage at the Made in America Festival in Philadelphia on Sept. 4. (Adam Schultz for Hillary for America)

Bill Clinton made a surprise appearance in Philadelphia yesterday, but it was hardly your average campaign stop. The former president showed up at Budweiser's "Made in America" festival, a Labor Day tradition with a reputation for its star-studded lineup. This year's included Coldplay, Rihanna, DJ Khaled and Chance the Rapper — artists handpicked by Jay-Z, the event's founder and curator.

After Clinton spent time registering concert-goers to vote, he was seen chatting up the stars. The photo that made waves across the celebrity-sphere was this:

We hope he remembered to wish her a happy birthday: Beyoncé turned 35 the same day, a fact fans were constantly reminded of by the many artists who gave her a shoutout on stage.

"Can you believe she's 107 years old?" Coldplay's Chris Martin asked the crowd.

The Clinton campaign later distributed additional photos of Bill talking with Beyoncé and greeting Jay-Z. The photos capture a glimpse of what it's like to hang around backstage with people who Run The World. But they're politically significant, too.

The unwritten message they send: Music's most powerful couple will be voting for Hillary.

Celebrity endorsements are a time-tested political maneuver, and for a campaign that hopes to wrangle every last woman, minority and young person into the voting booth, there is perhaps no figure as influential as Beyoncé.

But "Queen Bey" has yet to formally endorse Clinton. It is assumed the two are aligned because Beyoncé appeared at a Clinton fundraiser in May. The next day, the campaign seized on the opportunity to woo the Beyhive by tweeting out what appeared to be a screenshot of a cellphone photo of Beyoncé at the event.

"Say you'll Bey on Team #Hillary2016, too," they wrote.

Yet there was no photo of the candidate and the Queen together, nor did the event appear on any of Beyoncé's social-media accounts.

Soon after, Hillary Clinton told Ellen DeGeneres how much she liked Beyoncé's visual album, "Lemonade."

"I really believe in making lemonade out of lemons," she said.

Then Leah Daughtry, CEO of the Democratic National Convention, told Refinery 29 that she was hoping Beyoncé would "fly over for a night" from her world tour to attend the DNC. She never appeared.

The Knowles-Carter family has been staunch supporters of — and seemingly friends with — the Obamas, appearing at their campaign events, inaugurations and birthday parties. Beyoncé is also vocal on issues that have been a focus of this election, such as police brutality. It would hardly be out of character for her to take a stand for Hillary. But two months away from the election, she has stayed quiet on the 2016 candidates.

Was Bill Clinton hoping to change that by stopping by on Bey's birthday?

Maybe — or perhaps he's just a big Chance the Rapper fan. Reuters captured this photo of the former president's expression during the Chicago artist's set:

Former U.S. president Bill Clinton applauds to Chance the Rapper during the fifth annual Made in America Music Festival. (Mark Makela/Reuters)

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