Here’s the deal: he’s in the room, so you options are either to talk about him or to pretend he’s not there.
You can put it off, you can discuss other things, you can hide for a while, but he ain’t going anywhere (heck, he doesn’t even fit through the door).
Imagine how you’ll surprise people when you – you who appear to have most to lose if you bring him up; you, whose plan seems to hinge on him not being there at all – call him out, describe just what he looks like, acknowledge that he could scuttle everything.
Better for you to name him and explain why it makes sense to barrel ahead regardless. It’s when someone else calls him out that you’ll be pushed onto your back foot and risk losing momentum.
It’s surprising to see the room’s reaction when the elephant is finally addressed. I used to work at a student newspaper at my college and some of the most productive meetings happened just because we discussed EXACTLY what we didn’t want to discuss. It was tense at first, but the talk needed to happen and as a result the situation improved immensely. Because of the lesson learned and the positive outcome, the elephant doesn’t seem so ominous anymore.