Note: Although this is written in the first person, I am relaying it from a person who wants to remain anonymous. I can ask for clarification if needed but no identifying details will be provided.
Background
I'm leaving a non-management position with a nonprofit at the end of the month. The nonprofit operates at several sites within the region and my position reports directly to the manager of the site. Typically, he and his team leaders would interview and score candidates for this position and he would make the final selection as the direct supervisor.
One of the candidates to replace me is a co-worker (and friend) who we all generally expected to take this position at some point. She has the skills and temperament for it and honestly would hardly need to be trained in anything besides the paperwork. The problem is that recently it's become clear both to myself and to the team leaders—and probably most of the office, honestly—that she and the site manager are having an extramarital affair.
Given the circumstances, the team leaders and I all agree that it would be completely unethical for him to directly supervise her (or to be involved in hiring her—basically giving her a promotion, in that it has more responsibility and pay).
The reaction so far
The team leaders have approached him directly and emphatically about this being a problem. He confirmed their suspicions but didn't seem to take their concerns seriously, saying he would take the fall if word got out. We are all surprised and upset because we have always known him as a very competent and ethical manager. This is far from the reaction we would expect, based on having worked with him for years.
As some sort of compromise, he asked me to replace him on the interview committee. He didn't come right out and say why but he was hinting, and I told him that I know what's going on and she should look for another job, but didn't elaborate.
We interviewed three candidates earlier this week. I tried to be totally objective in scoring their responses to the interview questions. While my co-worker did very well, an internal candidate from another site actually gave better responses and scored higher in my final accounting.
Unfortunately, the team leaders are so upset by what's going on that they decided to rate all of the candidates equally, to force our manager to take responsibility for making an ethical decision. Then when we discussed the candidates and I let them know my ratings, the team leaders rigged their scores so that my co-worker and the other internal candidate would be tied anyway.
The other candidate has a glowing reference from her manager at one of our other sites and very good performance metrics. Yesterday my manager said he was leaning toward the other candidate, but today he said he's decided to offer the job to my co-worker. He said there are "other reasons" for her to have it.
My problem
Everything about this is frustrating but I'm most unhappy with my manager's behavior. Even though I'm leaving at the end of the month, I don't want the site to suffer the consequences of his bad decisions down the road. He's even said that if he's found out, he'll claim that he coerced our coworker to keep her from getting in trouble, which is insane and maybe even criminal.
How can I decide whether to confront him about his unethical behavior, or just stay silent? What potential consequences are important for me to consider, if I'm not going to be working there much longer?
I've talked with the co-worker and I don't think she's really been considering the potential consequences either. They're both going through divorces so it's understandable they aren't thinking that clearly. Nobody has talked to upper management or the company lawyer about this so far although a confidante of mine has suggested going to the lawyer. I don't want to rat him out to the lawyers without confronting him, either. I don't think I'm at risk because I've behaved ethically, I have absolutely no authority in this position and I'm not going to be here for long. He already gave me a glowing reference for the job I'm leaving to take and I don't think he'd retaliate in the future.
If I have a goal here, it's to try to defuse the situation and prevent him from making some really bad choices that could drive away a lot of employees and seriously impact the entire program. At least half of the people in the office know about their relationship and the position and nobody is happy about it. The team leaders are really upset and have let him know but they don't seem to be able to solve it. Can I do anything? Should I do anything? I have never been in this type of situation before.