WASHINGTON - Former President George W. Bush returned to the White House for the unveiling of his official portrait Thursday, joining his successor President Barack Obama in a congenial ceremony that set aside their political differences. Obama credited Bush with going out of his way to make sure his transition to the presidency was smooth after the 2008 election. “President Bush understood that rescuing our economy was not just a Democratic or Republican issue, it was an American priority. I’ll always be grateful for that,” Obama said.Obama also told Bush he would never forget seeing him standing on the rubble of Twin Towers after the Sept. 11th attacks with a bull horn “conveying extraordinary strength and resolve” to Americans.Obama has framed his presidency —and his re-election campaign— as a rebuilding of America in the wake of Bush’s stewardship of everything from the economy to foreign affairs, according to media reports. But no political or personal differences figured in the two presidents’ remarks.Both Bush and his wife, Laura, had official portraits in the East Room unveiled Thursday afternoon. The ceremony also included First Lady Michelle Obama, Vice President Joe Biden, Jill Biden, former President George H.W. Bush and former First Lady Barbara Bush. The portrait ceremony is a presidential tradition marked by pleasantries but also political awkwardness.Obama said, “We may have our differences politically but the presidency transcends those differences.” He and Bush also traded jokes. “You left me a really good TV sports package,” Mr. Obama said, drawing laughter. “I use it,” he added.Bush thanked Obama for welcoming him back to the White House, and offered him some advice. He said when Obama is wandering the halls of the White House and sees Bush’s portrait, he’ll now be able to ask “What would George do?”Bush also noted how Dolly Madison saved the portrait of George Washington during the War of 1812. “Now, Michelle, if anything happens – there’s your man,” he said, nodding to his own portrait.Bush’s portrait shows him in a grey suit leaning on a chair in the Oval Office. Mrs. Bush’s portrait shows her in a blue down standing in the Green Room.