Vice President Biden has also been spotted at Phillies games, and his baseball loyalties are clear. He even told a group of reporters this summer that he would give a "free interview" to any reporter who was wearing a Phillies hat.
the Bidens were in attendance for a five-run ninth inning Phillies rally against the Pittsburgh Pirates at Citizens Bank Park on July 11 and met some of the players in the clubhouse after the game.
"We're great Phillies fans," said Biden, sporting Phillies cap. He noted to Phillies slugger Ryan Howard that while his wife was at the World Series clinching game, he had to miss it.
"They wouldn't let me come for security reasons," the the vice president told Howard.
But it is his wife who is the more visible and passionate fan.
This April she attended the Phillies season opener on the road against the Washington Nationals and even appeared at one point on the stadium's large screen trying to snag a foul ball.
The vice president knows that when it comes to baseball, he can't challenge his wife's loyalty.
At a DNC fundraiser at Boston's Fenway Park this summer, Biden was presented with customized Red Sox jersey ("VPOTUS" – Vice President of the United States - #2) and admitted he may have to hide it around the house.
"The fact of the matter is, I love your team but my wife's from Philly," Biden said. "I will wear this proudly as long as my wife is not around," adding that if his Phanatic Phillies fan wife saw him sporting the Red Sox jersey, "I'll be sleeping alone."
The Yankees took Game 2 on Thursday night in the Bronx, evening the best of seven series at one win apiece. Now the games shift to Philadelphia, and not surprisingly, Biden says she's confident that the home field will benefit her team.
"Just wait until they return to Philly!" Biden said. "The Phillies will win the series!"
They may have to do it without their No. 1 fan, though. As of now, she has no plans to attend any of the games in Philadelphia this weekend.
"I will be watching and rooting wherever I am," she said.
ABC News' Matthew Jaffe contributed to this report.