ST. LOUIS (AP) -- Washington University in St. Louis has a history of hosting presidential debates, so students trying to attract Sen. Barack Obama for a campaign appearance Saturday were disappointed to learn the school wouldn't go for it.

When word spread that Obama planned a St. Louis rally and a venue hadn't been announced, student supporters approached the administration this week to see if he could come to campus. The university, which is hosting a vice presidential debate on Oct. 2, said no. The university says because it can't accommodate all requests for campaign rallies without disrupting operations, it can't permit any.

"To make an exception for one or two campaigns would be to give the appearance of favoritism or partisanship, especially given the literally dozens of declared candidates currently seeking the nomination by several political parties," the school said in a statement Thursday.

The Obama campaign, for its part, said it had not approached the university seeking to have him speak there. "It was a total student effort," said spokesman Caleb Weaver. He said the campaign looked into several possible venues before renting the Edward Jones Dome downtown. Doors open to the public at 7 p.m. Saturday.

The president of Students for Barack Obama at Washington University, Kevin Wolfe, 19, of Chicago, called himself disappointed by the university's decision, but said he also understood that students had approached the school less than a week before a possible appearance.

He said logistical and security concerns raised by the university were valid. Wolfe said the university also told students because of its tax-exempt status, it needed to maintain its neutrality.

Robert Wild, assistant to the chancellor, said by law the school cannot show political favoritism, but that was not the reason for the administration's decision about campaign rallies. Nor was it the fact that the school is hosting the debate later this year, he said.

Wolfe hoped there would be a renewed discussion about what should be permissible on campus in an election season. Others called the university's position on the matter unfortunate.

Student Union President Neil Patel, 22, of Miami said in an e-mail he was not involved in the effort to attract Obama, but thought the appearance would have been of tremendous value to the student body.

"If we had the chance to bring in one of the major political figures of our time, and perhaps the rest of the candidates as well, we would have taken a significant step in educating our student body as they prepare to vote, many of them for the first time," he said.

Alumna Elizabeth Stolar, 38, recalled that when she was at Washington University vice presidential candidate Lloyd Bentsen appeared at a rally on campus during his 1988 campaign with Democrat Michael Dukakis.

The attorney who lives in Schwenksville, Pa., said she was very disappointed when she learned that such rallies aren't being allowed these days. She called them an exciting opportunity for students to become active in politics.

She said the university should welcome opportunities for political candidates to appear, especially before a presidential election, and didn't think they'd disrupt campus life.

"I find it very hard to imagine that every candidate is going to converge on the Wash. U. campus," she said.

Wild said he wasn't sure when the school first began its policy against campaign rallies on campus, but said in 1992 a campaigning Bill Clinton didn't speak on campus, but instead appeared in a nearby park.

Wild said an invitation to Republican presidential candidate Mike Huckabee, the former governor of Arkansas, was issued before he declared his candidacy last year, and said Huckabee was invited to speak about his book and not his political campaign.

The National Association of Independent Colleges and Universities, an association of private colleges and universities in Washington D.C. that includes the St. Louis school, said the IRS suggests that not-for-profit schools have a panel of speakers or, barring that, balance the views of one speaker with a second one.

"Most schools will try to make sure they balance a speaker out with another candidate," said spokesman Tony Pals.

He said Washington University's commitment to political discourse should be evident in its efforts to host the presidential and vice presidential debates in recent years. He said issue-driven forums, events surrounding the debates, and the chance to attend the debate itself will provide students with several opportunities to get more involved.