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AUSTIN, Texas — The five living former presidents put aside politics and appeared together for the first time since 2013 at a concert on Saturday to raise money for victims of devastating hurricanes in Texas, Florida, Louisiana, Puerto Rico and the U.S. Virgin Islands.

Democrats Barack Obama, Bill Clinton and Jimmy Carter and Republicans George H.W. and George W. Bush gathered in College Station, Texas, home of Texas A&M University, to try to unite the country after the storms.

Texas A&M is home to the presidential library of the elder Bush. At 93, he has a form of Parkinson's disease and appeared in a wheelchair at the event. His wife, Barbara, and George W. Bush's wife, Laura, were in the audience.

Grammy award winner Lady Gaga made a surprise appearance at the concert that also featured country music band Alabama, Rock & Roll Hall of Famer 'Soul Man' Sam Moore, gospel legend Yolanda Adams and Texas musicians Lyle Lovett and Robert Earl Keen.

The appeal backed by the ex-presidents has raised $31 million since it began on Sept. 7, said Jim McGrath, spokesman for George H.W. Bush.

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President Donald Trump offered a video greeting that avoided his past criticism of the former presidents and called them "some of America's finest public servants."

"This wonderful effort reminds us that we truly are one nation under God, all unified by our values and devotion to one another," Trump said in the greeting, played during the concert.

Four of the five former presidents — Obama, George W. Bush, Carter and Clinton — made brief remarks that did not mention Trump. The elder Bush did not speak but smiled and waved to the crowd. They appealed for national unity to help those hurt by the hurricanes.

"The heart of America, without regard to race or religion or political party, is greater than our problems," said Clinton.

The last time the five were together was in 2013, when Obama was still in office, at the dedication of George W. Bush's presidential library in Dallas.

There is precedent for former presidents joining forces for post-disaster fundraising. George H.W. Bush and Bill Clinton raised money together after the 2004 South Asia tsunami and Hurricane Katrina the next year. Clinton and George W. Bush combined to seek donations after Haiti's 2011 earthquake.

"It's certainly a triple, if not a home run, every time," said Brandon Rottinghaus, a political science professor at the University of Houston. "Presidents have the most powerful and prolific fundraising base of any politician in the world. When they send out a call for help, especially on something that's not political, they can rake in big money."

Former President George W. Bush, center, speaks as fellow former Presidents from right, Barack Obama, Bill Clinton, George H.W. Bush and Jimmy Carter look on during a hurricanes relief concert in College Station, Texas, Saturday, Oct. 21, 2017. LM Otero / AP

Amid criticism that his administration was initially slow to aid ravaged Puerto Rico, Trump accused island leaders of "poor leadership," and later tweeted that, "Electric and all infrastructure was disaster before hurricanes" while saying that Federal Emergency Management Agency, first-responders and military personnel wouldn't be able to stay there forever.

But Rottinghaus said ex-presidents are seen as less polarizing than the current president.

"They can't get away from the politics of the moment," he said of current White House occupants. "Ex-presidents are able to step back and be seen as the nation's grandfather."

Lady Gaga performs for the five former U.S. presidents, Jimmy Carter, George H.W. Bush, Bill Clinton, George W. Bush, and Barack Obama during a concert at Texas A&M University benefiting hurricane relief efforts in College Station, Texas, U.S., October 21, 2017. Richard Carson / Reuters

Hurricane Harvey slammed into Texas and Louisiana Gulf Coast as a Category 4 hurricane on Aug. 25, unleashing historic flooding in Houston and killing more than 80 people. Shortly thereafter, all five ex-presidents appeared in a commercial for a fundraising effort known as "One America Appeal." In it, George W. Bush says, "People are hurting down here." His father, George H.W. Bush, then replies, "We love you, Texas."

Hurricane Irma subsequently hit Florida and Hurricane Maria battered Puerto Rico, while both devastated the U.S. Virgin Islands.