David Miller, Toronto’s high-profile mayor, made the surprise announcement last Friday that he would not run for a third term next year. Miller says he had made the decision not to run back in 2007, and only just got around to letting everyone know, but that’s a little hard to believe, given that, according to some stories, many of his closest political backers only heard about Friday morning, just before he went public. There were even some people on the inside who only heard when Miller went in front of the mikes.

So why’d he do it?

Municipal politics are notorious for favouring incumbents – get in and, unless you are a complete bonehead, you are in for good. The mayor’s chair is only slightly more vulnerable to challenge, but in Miller’s case, he was being threatened with going against some big names, namely former opponent John Tory (who hasn’t yet found an election campaign he can’t lose, but whom Torontonians just might give a second chance to) and George Smitherman (the cabinet minister who, according to the Toronto Star, is already being shuffled out of cabinet in preparation for a mayoral run). After last summer’s garbage strike, and various smaller political brush fires, Miller’s polling numbers are in the basement – quite an accomplishment, given how popular Miller was for so long.

What did him in? Writing in the Toronto Sun, John Lorinc claims that Toronto is traditionally warmer to centre-right mayors, and that Miller “simply couldn’t shake his reputation as a lefty.” (Lorinc also notes, however, “that in the context of the politics of many global cities, Miller would rank as little more than a reluctant reformer.”)

Obviously, the garbage strike was the biggest bow against him, any there’s no doubt that Miller bungled things there, pissing people off on both sides of the issue, but given how much he actually accomplished, it’s hard not to see Miller’s unpopularity as simply a result of not meeting expectations that may have been impossibly high. Toronto, as it is now constituted, is a massive, sprawling entity, with a lot of warring factions – the suburbs vs downtown being the most significant. Miller swept into power as an activist mayor, but activists need to be pugnacious and iron-willed if they are to get anything done, and Miller was more a creature of municipal politics, where incrementalism and compromise are the rule, than he first appeared. (This is the same problem that plagues Jack Layton and the NDP; paradoxically enough, conservatives don’t often have trouble electing (right-wing) radicals into leadership positions.)

In short, you need to be more than a bit of an asshole to get some things done, and Miller wasn’t that kind of asshole.