Source. Confirmed here (M. Rowe from Ipolitics) among other places.
PS. On a related matter, don't get too excited by Coyne's column from yesterday, mourning how the CPoC's has lost its principles. He's been writing the same piece for years now. They still let him into their events, which means that being reamed by Coyne, for a CPoC hardcore, is a bit like being spanked by your grandma. It doesn't hurt that much. It isn't meant to.
Update: Dawg has some details that I missed, including the fact that Glen McGregor of the Ottawa Citizen was there and left the party in solidarity with Maher.