After learning the Senate ethics committee had scheduled unusual public hearings into the conduct of five senators accused of acting improperly on behalf of a savings and loan operator, Sen. John Glenn, D-Ohio, made a prediction to reporters.

"You people are going to have a ball, I can guarantee that," Glenn, one of the so-called Keating Five, said last month.The ball, with Sens. Alan Cranston, D-Calif., Dennis DeConcini, D-Ariz., Glenn, John McCain, R-Ariz., and Donald Riegle, D-Mich., facing the music, starts Thursday and could last several weeks.

The triallike proceedings before the Select Committee on Ethics promise to blossom into a public spectacle replete with several juicy political themes, including conflicting allegations of corruption and influence-peddling by elected officials and claims of innocence and indignation.

"The message here is going to come down to one of the institution's own credibility," said Fred Wertheimer, president of Common Cause, the public interest group that initiated the complaint against the five senators.

"I think there are larger questions involved here and they go to what the Senate sees as proper and acceptable conduct for a United States senator," Wertheimer added. "Bottom line, that's what the committee's going to be ruling on in this case . . . Is there a willingness to hold colleagues accountable for improper conduct when it occurs? Or does the Senate take care of its own at the expense of holding members accountable?"

The five are under investigation for intervening with federal regulators on behalf of thrift executive Charles Keating and his failing Lincoln Savings and Loan during the mid-1980s, when the quintet received a total of $1.3 million in contributions to their campaigns and political causes.

Meetings that the senators held with former officials of the Federal Home Loan Bank Board raise questions about whether the lawmakers violated a Senate rule prohibiting senator from contacting federal regulators outside of official channels.