Don Meredith is the senator whose conduct was so egregious that it is making senators draw an indelible line: They appear set to concede, for the first time, that their privileged positions can be forfeited for bad behaviour.

Think what a precedent this could make for the Senate, the institution best known for its utter lack of accountability, one that has lived through a litany of scandals. It would mean it is possible for a senator to go too far and pay for it with their plush seat.

It took 150 years to get here. But some members of the Red Chamber will still be shocked at the prospect. On Tuesday, the Senate's ethics committee recommended that Mr. Meredith, who maintained a sexual relationship with a teen, be expelled – and it asserted, for the first time, that the Senate does have the power to boot one of its own, even if the senator has not committed a crime.

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Globe editorial: The troubling case of Don Meredith, and senators who just won't quit

Mr. Meredith now has five days to decide if he will appear in person in the full Senate chamber to make one last appeal against his expulsion. His lawyer, William Trudell, said he does not know yet whether he will. "He's going to meet with family," Mr. Trudell said. "That's important to him, to meet with his family and decide how to proceed."

Mr. Meredith's behaviour, spelled out in a report by Senate ethics officer Lyse Ricard, is now infamous.

He met a teen, identified in Ms. Ricard's report only as Ms. M, when she was 16 and he was 48, handed her his Senate business card with his cellphone number, and then developed a sexual relationship that included touching and Skype chats in which Ms. M undressed and Mr. Meredith masturbated. Mr. Meredith insisted the two did not have intercourse until after Ms. M turned 18; Ms. Ricard reported that Mr. Meredith briefly penetrated the young woman – calling it a "teaser" – when she was 17. Since the age of consent is 16, Ottawa police laid no charges.

But Ms. Ricard still found Mr. Meredith's behaviour did not meet the standards demanded by the Senate's ethics code. The ethics committee decided his behaviour tainted the dignity of the Senate, and that allowing him to keep his seat would damage the public trust so severely that the function of the Senate would be impaired. "Senator Meredith," said the ethics committee chair, Raynell Andreychuk, "misused his privileged position as a senator."

Because they are unelected, Ms. Andreychuk said, senators have to live up to the public trust both in their public and private conduct. It would certainly be a sea change if the Senate backed up that notion with the threat of potential expulsion.

It has become a test for the Senate, an institution that is trying to redeem its image, and Mr. Trudell is trying to make the case that his client has been caught up in that.

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Mr. Meredith had proposed to the committee that instead of expulsion, he should be suspended for one to two years without pay. Mr. Trudell argues that expulsion has to be reserved for a senator convicted of a crime, or for "the most egregious conduct, where someone is without character support, [and] doesn't accept responsibility or accountability." He said Mr. Meredith acknowledged his mistake, engaged with the ethics committee and 22 people wrote character references. And he has already been punished with public disapproval and condemnation in the press, Mr. Trudell said: "That stings."

But there is a reason Mr. Meredith suffered that. He does hold a privileged position. His conduct has been an affront to the already-questionable dignity of the Senate.

This was a self-described youth advocate who made speeches about protecting youth from internet luring, but encouraged a 16-year-old Ms. M to undress over Skype, telling her "this is what adults do." He promised to put Ms. M on a committee honouring the first black recipient of the Victoria Cross. Under investigation, he dodged, telling Ms. Ricard, for example, he did not remember if he masturbated during Skype chats. The Senate ethics committee found Mr. Meredith did not exhibit responsibility until Ms. Ricard's damning report was done.

Mr. Meredith, as it turns out, makes a pretty compelling test case. Now it will test whether the senators are willing to draw a line they cannot cross.