NC for this. I started a new job 4 months ago and one of my co-workers has taken against me. I have more training and experience than they do and the senior managers have indicated they are thinking about promoting me. They have also said they think co-worker is intimidated by me. Today in a meeting where no manager was present, this person was foul to me, indicating that they had gone to a senior about something I did and that person agreed I was wrong. I pointed out that my decisions had been discussed with the seniors at the time, they agreed with my proposed course of action, and this was all documented. Nasty co-worker semi- backed down saying something about mixed messages being given. They blew up at me so quickly and the tone they used was really aggressive that a few people checked in after and asked if co-worker was always like that with me. It's not the first incident but was the most blatant.
This is where it's complicated - this person is the friend of a friend of the senior mentioned. I raised it (in a general way, mentioning no names) with the other senior today, who backed my decision making again. I am due to meet with the other in a few weeks - would you mention this to them? On one hand I don't want to put up with this nonsense, on the other, I really like the actual job and was hoping this was somewhere I could stay for a while.