Maybe he's running for the BC Liberal Leadership...
Sadly, he's not resigning in furor over the potash deal. There isn't a hidden scandal involving Chinese pandas. He's not in any way involved with Julie Couillard.
Rather, Jim Prentice will resign as an MP to take a Vice-President position at CIBC. I'm not up on my conflict-of-interest rules, but I'm sure the Tories will assure us this doesn't breach any ethical guidelines and the Liberals will assure us it most certainly does.
Well, that's the official explanation for his departure. The more truthful one is that being Stephen Harper's environment minister is a miserable job that is quietly killing Prentice's soul and/or leadership ambitions. So, bon voyage Jim - we'll look you up when Stephen Harper or Ed Stelmach announce their resignations.
As for what it all means, we'll have a by election in Calgary - I'll leave it to the good people at Pundits Guide to speculate on timing, though I suspect it will get rolled up with the other two by elections we have coming down the pipe (one for a Bloc seat in Quebec, the other in Jay Hill's BC riding). Being Calgary, (spoiler alert!) the Conservatives will win that by election (though to downplay expectations the PMO will let Jane Taber know it's the Liberals' seat to lose).
I know it won't happen, but if anyone wants to speculate about Dave Bronconnier making a jump to federal politics, this would be a good time to do that. Calgary Centre-North one of the most Liberal-friendly ridings in the city, a popular moderate incumbent is leaving, and a by election entry point would let Bronconnier win on his name rather than on the Liberal brand. Toss in frustration among the Tory base over wild spending, and this is about as good a chance as Bronco's ever going to get. Hell, the city's even in a "let's go wild" kind of mood, having just elected Naheed Nenshi as mayor. Maybe they'd be crazy enough to vote in a Liberal!
But assuming Bronco doesn't run, the more interesting side effect of this is the inevitable Cabinet shuffle speculation we're about to be subjected to. John Baird will act as interim environment minister but assuming "interim" actually means "interim" (and this isn't like "Canada's new government") someone else will eventually inherit the portfolio.
As mentioned above, it's not exactly a prize job. I have no clue who Harper will choose, though I'm guessing it's likely someone whose leadership ambitions Harper is looking to crush.