The former president will be eulogized by his son George, the 43rd president, along with former Canadian Prime Minister Brian Mulroney; Alan Simpson, a former senator from Wyoming; and Jon Meacham, a historian who wrote "Destiny and Power: The American Odyssey of George Herbert Walker Bush."
Mulroney became close friends with Bush as they negotiated the North American Free Trade Agreement, one of several aspects of Bush's legacy that Trump has excoriated.
Bush's casket lay in state under the soaring Rotunda at the U.S. Capitol since Monday night. After an official arrival ceremony with members of Congress on Monday, members of the public jostled in long lines on Tuesday, some waiting more than three hours to pay their respects to a patrician leader known for his ethics and decency.
Among the mourners Tuesday was Bob Dole, Bush's former political rival. Wounded in World War II, the 95-year-old Dole struggled to rise from his wheelchair and offer a salute to Bush, a Navy pilot who was shot down over the Pacific during the war.
In addition to competing in the 1988 Republican presidential primary, Bush and Dole helped to rebuild and define the Republican establishment, especially after Nixon was forced to resign in disgrace in 1974 amid the Watergate scandal.
Bush served as President Reagan's vice president for two terms, and then as president from 1989 to 1993. He led America into war to oust Iraqi troops from Kuwait, and helped guide the peaceful dissolution of the Soviet Union and the reunification of Germany after the Berlin Wall tumbled, as the Cold War finally drew to a close.
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But Bush's deft hand in foreign affairs failed at home, where he saw his popularity plummet as the economy soured. He lost after one term to Bill Clinton, a Democrat, but Bush's popularity grew as the decades passed and his achievements became more clear.
Bush's remains were taken from the Capitol on Wednesday morning and driven to the National Cathedral, an iconic Neo-Gothic church. As president, the elder Bush attended a ceremony to mark the cathedral's completion after 83 years of construction, though decorative work continued.
The funeral was expected to last about 90 minutes and feature readings from three of his grandchildren: Ashley Bush, Lauren Bush and Jenna Bush Hager.
The casket will be flown to Houston for a second funeral on Thursday before Bush is buried in College Station, home of the George Bush Presidential Library and Museum at Texas A&M University.