I think the best reference point to look at would be the most recent “real” recession - the one of the early 90s. So let’s take 1990 as the starting point and look at the 11 provincial (and federal!) elections that happened after that point, to see how the incumbents did.
Re-Elected: 5 (PEI, NF, NB, MN, AB)
Defeated: 6 (CAN, NS, PQ, ON, BC, SK)
So a little over half went down in defeat. Of course, Klein's bitter 1993 victory may be a "technical" win but, by Alberta standards, it's really a loss for the incumbents. Of course, there were obviously other factors in play...I have doubts the BC Socreds, federal PCs, or Quebec Grits could have hung on, even in the best of economic situations.
Comparatively, if we take 1995 as our base line, 8 of 11 governments survived, if we look at 2000, 7 of 11 survived, and if we look at 2005, 6 of 10 survived (BC pending...).
So, what’s the moral? I dunno. Politics is a complicated game. And we don’t even know how bad this recession will be. All we can really say is that governing through tough times is a political challenge, but that it’s not necessarily fatal.