Thomas V. Mike Miller needs to stop acting like Nathaniel Oaks’ lawyer and start acting like the president of the Maryland Senate.

It’s good that Mr. Miller — begrudgingly, belatedly — will ask the General Assembly’s Ethics Committee to investigate the federal corruption and obstruction charges against Senator Oaks. But his continued insistence that any legislative action should be subservient to the criminal proceedings is not only wrong but diminishes the integrity of an institution he professes to revere.

It is inexplicable that Senator Miller displays so little concern that one of those whotook up a red leather chair in the Senate chamber yesterday reportedly admitted to taking bribes in exchange for abuse of his position. Senator Oaks was forced from office a generation ago after a conviction for stealing campaign funds for personal use, and the details of the indictment against him now suggest his corruption only grew more ambitious and sophisticated in the intervening years. Gov. Larry Hogan has called on Mr. Oaks to resign, yet Mr. Miller, the self-appointed guardian of the Senate, not only will not do that but also repeatedly insists that Mr. Oaks is “cloaked in a shroud of innocence” and that he should not be removed from office before his April trial.

Mr. Miller is right that Mr. Oaks, who denies the charges, is innocent until proven guilty beyond a reasonable doubt. Indeed, the accusations against him are only that until and unless upheld in a court of law, even if the FBI says it caught him accepting bribes on tape and that he admitted to his wrongdoing in an attempt to strike a deal as a cooperating witness before later reneging and warning off another potential target of the investigation. But those are the standards for criminal convictions, not those by which the General Assembly of Maryland must decide whether a member is fit to serve.

Remember, Senator Oaks is not merely holding his seat. He is showing up and voting. To say the Senate can’t do anything about that before the criminal trial concludes is like arguing an alleged embezzler not only can’t be fired before he is convicted but must also be allowed to man the cash register in the meantime.

Senator Miller understood that 20 years ago when then-Sen. Larry Young was accused of using his position to profit himself. The legislature did not then wait for Mr. Young to be indicted much less tried before launching its own investigation or coming to the conclusion that the West Baltimore Democrat should be expelled.

When Mr. Young did go to trial, the jury was not influenced whatsoever by the Senate’s action. His attorney did not have to call a single witness to persuade the jury to acquit. After the verdict, Mr. Miller expressed no regret at the Senate’s actions, saying at the time that the Senate’s process was distinct and focused on its own issues and standards.

But he forgot that somewhere along the way, having waited until after a jury acquitted Sen. Ulysses Currie on charges related to the abuse of office to conduct an ethics investigation, which led merely to censure for the Prince George’s lawmaker.

Mr. Currie’s defense was, essentially, that he was too dumb to be corrupt, that he didn’t realize what he was doing was wrong. The FBI, by contrast, says it has tapes of Mr. Oaks taking envelopes of cash and evidence that he coached alleged co-conspirators on tactics to avoid producing incriminating evidence. He is charged with taking $15,300 in cash payments from an FBI informant, and witnesses in the case say he took much more than that over the years. Now his attorneys claim that the investigation into Mr. Oaks was part of a broad probe into possible corruption in the Baltimore City Council and Maryland General Assembly. Federal authorities say he had promised to cooperate in an investigation into an unnamed associate and recorded himself taking $2,600 in cash under the table of an Annapolis restaurant last year from the person before promising to talk to colleagues about a pro-bail bonds industry bill. The FBI further says Mr. Oaks tipped that person off to the probe during a St. Patrick’s Day party at an Annapolis bar. A witness in the case says Mr. Oaks was not the only lawmaker who took bribes from the bail bonds industry. This is not something Senator Miller thinks merits immediate action?

Senator Miller says he is worried that if the legislature gets ahead of the criminal proceedings, it would prejudice an as yet unempaneled jury of people who may or may not be paying the slightest attention. Past experience with which he is intimately familiar suggests that is not the case. What he is definitely doing, though, is prejudicing the 46 other Senators against expulsion.

Mr. Oaks, who showed up for the last day of the 2017 legislative session immediately after he was first indicted, clearly lacks the shame necessary to do the right thing for his constituents and the institution he has served for 30 years and step down. His continued presence in the Senate will tarnish the institution’s reputation in the public’s eyes for the next 90 days. A refusal by his colleagues to do anything about it will complete the job.