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R. Sargent Shriver, the ever-upbeat Kennedy in-law who served as the nation's first Peace Corps director and later led a national assault on poverty, was remembered Friday evening as an energetic idealist who left a legacy of public service.

"Sargent Shriver was the kindest, most cheerful, most optimistic person I knew in 50 years of public life," said former South Dakota Sen. George McGovern, the 1972 Democratic presidential nominee, referring to his running mate that year. "It's remarkable that those virtues could all be combined in one person. I don't ever recall seeing him down in the dumps. He must have had days like that, but nobody ever saw them if he did."

Hundreds filled Holy Trinity Catholic church in Washington to pay their respects at a wake to Shriver, the brother-in-law of President John Kennedy and the late Sens. Robert and Edward Kennedy. He died Tuesday at a Maryland hospital at 95, eight years after announcing that he had Alzheimer's disease.

Vice President Joe Biden and former President Bill Clinton were scheduled to speak at a funeral Mass on Saturday at Our Lady of Mercy Parish in Potomac, Md. First lady Michelle Obama and Oprah Winfrey will also attend

On Friday, some of Washington's most prominent figures filed past the casket and photos from Shriver's life to extend condolences to family members including his daughter, former NBC reporter Maria Shriver; her husband, California Gov. Arnold Schwarzenegger; and Shriver's four sons.

Some of those who attended the wake had met Shriver through his work and others only knew him by his reputation.

"He was the finest man I think I ever met in my life," said Gene Theroux, 72, of Loudoun County, Va., who worked at the Office of Economic Advancement where Shriver served as director in the 1960s. "He was full of positive energy."

"He took a thankless job at President Johnson's request to run the poverty program," Theroux said. And though many of the programs were unpopular, Shriver was able to bring people together to get them off the ground, he said.

The outpouring of praise for Shriver and support for his family since his death on Tuesday was extraordinary because he had not been in the public eye for years, said Bill Moyers, a journalist and former Johnson aide who wrote the foreword to a Shriver biography and worked with him at the Peace Corps.

"I believe it happened because...he gave us permission in the 1960s to be idealists," he said. "This distressed, this disillusioned country ... knew intuitively when the word came of his death that it was OK to be an idealist. He was — as a documentary about him said — the American idealist."

The descendant of a prominent Maryland family, Shriver was also remembered in eulogies by House Minority Leader Steny Hoyer of Maryland; former U.S. Sen. Chris Dodd of Connecticut; C. Payne Lucas, former president of development aid at nonprofit Africare; Vanity Fair writer Maureen Orth; and Colman McCarthy, a journalist and former Shriver speech writer.

Also attending were Massachusetts Sen. John Kerry, Health and Human Services Secretary Kathleen Sebelius, AOL co-founder Steve Case, musician Wyclef Jean, White House senior adviser David Axelrod, and singer and actress Vanessa Williams.

A businessman and lawyer, Shriver helped his late wife, Special Olympics founder Eunice Kennedy Shriver, run the organization that allows disabled people to participate in sports. She died in 2009 at age 88. The couple had 19 grandchildren.

Shriver will be buried late Saturday in the same cemetery in Hyannis, Mass., as his wife, according to Rev. Daniel W. Lacroix, pastor at St. Francis Xavier Church.

"We take comfort knowing that Mummy and Daddy are together now in heaven," Maria Shriver told the gathering, as her four brothers stood behind her. "While we miss him, he talked about how he was excited to go to heaven. Living the last year and a half without Mummy was difficult for him and that's where he wanted to be."

Known as "Sarge," Shriver helped fulfill one of President Kennedy's campaign promises to start the Peace Corps and ended up building an international institution. He later ran the War on Poverty, part of President Lyndon Johnson's Great Society.

Shriver was McGovern's running mate in the 1972 presidential election, but the Democrats lost in a landslide to President Richard M. Nixon. In 1994, Shriver received the Presidential Medal of Freedom, the nation's highest civilian honor.