President Barack Obama is set to host Pope Francis at the White House for the first time Wednesday, warmly embracing the Catholic pontiff seen as both a moral authority and potent political ally. The packed and bedecked South Lawn will echo to strains of the Pontifical Anthem and a thundering 21-gun salute, as the 78-year-old is afforded a full ceremonial welcome on his historic maiden visit to the United States. Washington -- a city that ordinarily shrugs its shoulders when presidents, queens and sheikhs roll through town -- has been enveloped in Pope-mania and so has the White House. Obama himself made an exceedingly rare trip to the airport to meet the Argentine's plane Tuesday, bringing his wife, daughters, Vice President Joe Biden and his extended family to underscore the point.