I imagine that since Paul Martin was dubbed "Mr. Dithers" by The Economist, it was inevitable that the Liberals would try and hang a nickname on Stephen Harper just to even the score. This is the first time I've seen this one, though.
In an article about the National Citizens Coalition (which as far as I can tell is neither national nor a coalition of citizens, exactly) expressing its dismay at the way Harper seems to be moving to the left, Dithers' communications director Scott Reid is quoted thusly:
"Mr. Nicholls is frustrated that Stephen Harper has turned into Mr. Muzzle because he believes in the extreme policies they're trying to conceal," Scott Reid said.
"Canadians are frustrated with Mr. Muzzle because they just want to know what it is he is working so hard to keep hidden."
Mr. Muzzle? I don't think it'll catch on. Try harder, Scott.