So many people are expected to attend the memorial service for Sen. Paul Wellstone, his wife and daughter and three campaign workers that the Williams Arena on the University of Minnesota campus may not be big enough.

The 14,000-plus seats in the University of Minnesota Gophers men's basketball arena is unlikely to accommodate the 20,000 people expected at the public memorial, so university officials said they will also open the adjacent Sports Pavilion to accommodate 5,000 to 6,000 more.

Since the event is supposed to be a celebration of the life of Wellstone and the others, organizers are trying to make it less somber than the usual memorials for national leaders.

"There will be speeches, people will be eulogized, there will be music -- there will be remembrances of everyone," said Allison Dobson, a spokeswoman for the Wellstone family. "There will be a formal program, but at the same time, it's not going to be stuffy. I don't think it makes any sense, given who these people were. We want to put together something to celebrate the lives of these six beautiful people."

But observers can expect some pageantry at the service for Wellstone, 58; his wife, Sheila, also 58; their daughter, Marcia Wellstone Markuson, 33; and campaign aides Will McLaughlin, 23, Tom Lapic, 59, and Mary McEvoy, 49.

Former President Bill Clinton is expected to attend as are former Vice President Al Gore and his wife Tipper.

Campaigning in Michigan on Monday, Gore called Wellstone "the most energetic and influential leader on mental health care in this country." Tipper Gore was an advocate of mental health issues while second lady.

Dobson said that most members of the U.S. Senate are also expected to attend, but she could not confirm whether President George Bush or Vice President Dick Cheney would attend.

On Monday, several senators gathered on the Senate floor to eulogize Wellstone and introduce a resolution expressing the Senate's "profound sorrow and deep regret" about his death as well as the others on the flight.

Wellstone, one of the Senate's most liberal members, "worked tirelessly on behalf of America's veterans and the less fortunate, particularly children and families living in poverty and those with mental illness," the resolution said.

"He was respected by people who didn't agree with him because they knew that he was speaking from his heart, speaking from his soul, speaking what he truly believed," fellow Minnesota Sen. Mark Dayton said.

Wellstone's desk in the back row of the Senate chamber was draped in black felt with a fresh flower arrangement on top. Only a handful of senators were in attendance since Congress is in recess while members campaign for re-election.

Sen. Christopher Dodd, D-Conn., noted that Wellstone "rubbed some people the wrong way" when he first came to Washington in 1991 because he was determined to change the world. "These very people became the people who cared most about him in many ways in the final analysis because they realized that everything he said and everything he did was not about himself but about the people he wanted to represent."

"He had courage," said Sen. Barbara Boxer, D-Calif. "Paul Wellstone could not vote against his conscience."

While Tuesday's gathering is not expected to be festive, Dobson said several music groups have offered to perform and the service would be informal, as Wellstone would likely have wanted.

"People can expect lots of music from Minnesota groups, probably including Native American, Hmong and African-American groups," she said. Several choirs will sing.

The list of speakers had not been completed by Monday night, though some sources said Monday that former Vice President Walter Mondale may speak at the memorial.

Preparations also were in the works for security and traffic concerns that accompany a program that was to start around 6:30 p.m. and last about three hours.

"It's quite a large task. There are folks working on this literally around the clock," Dobson said. "People can expect very high security, not because we don't want people to come -- we want everyone who can to be involved -- but people should plan accordingly. It might include metal detectors and searches of bags, so people should come early."

While Minnesota's high weather temperatures were expected to hover around 42 degrees on Tuesday, Dobson said that the overflow accommodations may not be enough and plans were in the works to have at least an audio feed outside for those willing to bear the cold to be there.

Wellstone's death came just 11 days before the midterm election in which he was running for a third term in a neck-and-neck race against former St. Paul Mayor Norm Coleman.

The state Republican Party has challenged Mondale, the presumptive nominee, to a series of debates, angering Democrats and even some Republicans who said it is disrespectful to cast a challenge before Wellstone has been laid to rest and a replacement formally named.

"I understand that these are stressful moments for everyone but I do think the sensitivities of the Wellstone family should be respected," said former Republican Gov. Arne Carlson in a letter.

But Democrats were doing their own low-key politicking Monday. Former U.S. Rep. and Minnesota Mayor Donald Fraser said Tuesday night's service should inspire mourners to carry out the work championed by Wellstone, his wife and the campaign.

"It seems to me that the public response to [his death] is greater now [because of] the war issue," Fraser said. "Clearly for some people, the poignant question being asked at this time was on the Iraqi issue. And they tie it very closely to Wellstone as one of the people to speak out against it."

Pilots Richard Conry, 55, and Michael Guess, 30, also died in Friday's plane crash near Eveleth but were not being eulogized at Tuesday night's service.

Fox News' Steve Brown and The Associated Press contributed to this report.