Oct. 30, 2009— -- Before game one of this year's World Series between the New York Yankees and the Philadelphia Phillies, Jill Biden strode out onto the field at Yankee Stadium to participate in a pre-game ceremony honoring America's veterans.
The vice president's wife, walking alongside first lady Michelle Obama and Yankees legend Yogi Berra, sported a maroon jacket with "World Series" emblazoned across the chest -- appropriately neutral attire to avoid a Bronx cheer from the Yankees fans, given Biden's status as a diehard fan of the Philadelphia Phillies.
She may be better known as the college professor wife of the Vice President Joe Biden, an advocate for military families and a staple on the campaign trail last year, but now that the Fall Classic is underway, Jill Biden may become known as the biggest, most loyal Phillies fan.
Her husband declared her the Phillies' "most rabid," fan and he knows firsthand how deep her loyalty runs.
Last year, Biden logged thousands of miles on the campaign trail with her husband, but with just six days to go before Election Day, the potential for a World Series title lured her back to her hometown.
"I gotta tell ya, my wife, I'm on the campaign trail, she says, 'Joe, I'm going to the Series.'" then-Sen. Joe Biden said of his wife's decision to go home and watch her team.
On Oct. 29, 2008, after anxiously waiting out a two-day rain delay, Biden and her granddaughter Maisy joined 45,000 towel-waving fans in South Philadelphia to watch in person as her Phillies beat the Tampa Bay Rays to win Major League Baseball's championship.
The World Series title was just the second for the Phillies franchise and ended a 26-year championship drought in that sports-obsessed city.
The vice president's wife told ABC News it was "exciting" to be there when her team won the title. Last year she called that night "one of the best nights" of the campaign.
Biden Recalls Summer Nights with Her Father
Biden, a native of Willow Grove, Pa., a Philadelphia suburb, said she's always been a fan of her hometown sports teams and counts watching Phillies games with her father on summer nights as some of her greatest memories.
"I was a little girl," she told ABC News, recalling watching games on the family's black and white Philco TV. "It was a great father/daughter memory for me."
Her favorite current Phillie is all-star shortstop and form National League MVP Jimmy Rollins. On the eve of the election last year, Rollins joined the Bidens at a rally in South Philadelphia, just days after the Phillies won the World Series.
The shortstop revved up a crowd of over 2000 at Marconi Plaza and presented then-Sen. Joe Biden with a Phillies home jersey with "Biden 08" on the back.
"I will never forget the night before the election last year we were at an 11 p.m. rally in Philadelphia, [Rollins] introduced me," Biden said. "He was for our team, our ticket, in the icy cold. It was so great, there was so much excitement in the air."
After Rollins gave his endorsement to the Obama/Biden ticket, Jill Biden took the stage sporting a red Phillies warm-up jacket and waving a white Phillies towel.
"One of the best nights of this campaign was watching the Phillies win the series," she told the crowd that night as she introduced her husband.
"This woman bleeds red," her husband said as he took the mic.
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."
Jill Biden Picks Phillies to Win the Series
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.