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Michelle Obama and three former first ladies were among dignitaries heading to California to pay tribute to Betty Ford at a bipartisan funeral focusing on her twin passions: politics and her world famous Betty Ford Center for substance abuse and alcohol treatment.

The casket containing the former first lady's body arrived late Tuesday morning at the Southern California desert church where she and the nation's 38th president worshipped.

It was to be followed into the church a short time later by numerous dignitaries, both Republican and Democrat, including a former president.

Ford, who died at the age of 93 on Friday, had mapped out plans for Tuesday's ceremony at St. Margaret's Episcopal Church, including who would deliver her eulogies.

She chose former first lady Rosalynn Carter and journalist Cokie Roberts as speakers along with a former director of the Betty Ford Center.

Mrs. Obama, Nancy Reagan and Secretary of State Hillary Rodham Clinton also planned to be there. And the former first lady of California, Maria Shriver, said she would attend.

A spokesman for former President George W. Bush said he will be attending the California service and will convey condolences on behalf of his wife, Laura, who can't attend. Former President Bill Clinton canceled plans to attend due to mechanical problems with a plane he was to fly on.

Other dignitaries who confirmed they would attend were President Richard Nixon's daughters, Tricia Nixon-Cox and Julie Nixon Eisenhower; President Lyndon Johnson's daughters, Lucie Baines Johnson and Lynda Bird Johnson Robb; and Robb's husband, former U.S. Sen. Charles Robb.

Following the funeral, members of the public were to be invited to file past her casket and sign a guest book until midnight.

A second funeral will be held Thursday in Grand Rapids, Michigan, where Gerald Ford is buried at his presidential museum. Former first lady Barbara Bush is expected to attend that event.

California Highway Patrol motorcycles and squad cars escorted the hearse and family members to Tuesday's service in four black sedans and six SUVS.

The hearse pulled up to the side entrance of St. Margaret's Episcopal Church in Palm Desert at 11:20 a.m. and was carried inside, followed by about two dozen mourners, including family members.

Before the casket's arrival Palm Desert residents took advantage of the pre-dawn cool, on a day in which the temperature was expected to reach 102 degrees, to walk dogs, jog and reflect on Betty Ford's life.

"I don't know where a lot of people would be if it weren't for her," said Randy Gaynor, 47, a recovering alcoholic. "There's been a lot of first ladies and they did a lot of things, but this will be long remembered after she's gone."

Media satellite trucks lined a street near the church and TV cameras crowded big-rig flatbed trucks across the street.

A program prepared for the service featured a picture of Ford, the Emily Dickinson poem "If I Can Stop One Heart From Breaking," and the words, "The family thanks you for your support," followed by the signatures Mike, Jack, Steve and Susan, Ford's four children.

Jack and Michael Ford were to read passages from the Old and New Testaments of the Bible.

Speakers were expected to discuss politics, the White House and Ford's impact on substance and alcohol abuse treatment.

Ford, the accidental first lady, was thrust into the White House when Nixon resigned as president on Aug. 9, 1974, and her husband, then vice president, assumed the nation's highest office. Although she never expected nor wanted to be first lady, she quickly embraced the role, reshaping it with her plain-talking candor.

Roberts said Ford asked her to give a eulogy five years ago and specified it should be about the power of friendship to mend political differences even in these hyper-partisan times.

Roberts, a commentator on National Public Radio and member of a noted political family, said Ford asked her to talk about a time in Washington when Democrats and Republicans could be friends and partisan politics did not paralyze government.

It was that way, Roberts said, when her father, Democratic Congressman Hale Boggs, was House majority leader and Republican Gerald R. Ford was House minority leader. She said they could argue about issues but get together as friends afterward. The two families became close as did the Ford and Carter families, despite Jimmy Carter defeating Ford in the 1976 presidential election.

Carter spoke at Gerald Ford's funeral in 2007. The two families were so close that before his death, Ford asked the Carters to join his wife aboard Air Force One, which flew his body to its final resting place in Grand Rapids.

"Mrs. Ford was very clear about what she wanted me to say," Roberts said. "She wanted me to talk about Washington the way it used to be. She knew there were people back then who were wildly partisan, but not as many as today.

"They were friends and that was what made government possible," said Roberts, adding that the topic seems particularly appropriate this week when the two parties are divided over dealing with the national debt ceiling.

Roberts said she expects Rosalynn Carter to talk about life in the White House and the important role of first ladies in "greasing the wheels" for their husbands' accomplishments by forging bipartisan friendships.

Former Betty Ford Center official Geoffrey Mason will also speak. Mason, a former member of the center's board of directors, is expected to extoll Ford's vision and determination in building a substance abuse and alcohol treatment center after her own recovery.

On Wednesday, her body will be flown to Grand Rapids where another church service Thursday will feature remarks by Lynne Cheney, wife of former Vice President Dick Cheney, and historian Richard Norton Smith.

Later Thursday, her body will be interred at the presidential museum along with her husband on the day that would have been Gerald Ford's 98th birthday.