I would seriously suggest that the NDP and Liberals in Alberta merge. It makes them competitive enough so that strategic voting wouldn't even be necessary to stop Wildrose, at least in most urban seats. Plus if the left has near zero presence seat-wise, the PCs will be more inclined to cater right to fend off Wildrose. If BC Liberals and the Sask. Party pulled off mergers so could they.
There's pretty much no way the Liberals and NDP would consider and electoral pact/coalition, never mind a merger.