I find it interesting how over the last 40 years the total votes for the PCs in Alberta has remained relatively stable. From 1975 to 2008 the PC total vote tracked somewhat closely to the total vote. It is in 2012 and 2015 that this pattern changed. The PC vote remained in their traditional band but the total number of voters increased dramatically
What this says to me is that in 2012 a whole bunch of social conservatives came out to vote for Wildrose that had not been voting. At the same time traditional Liberal voters seem to have gone to the PCs in that election.
In 2015 it seems that several hundred thousand left of centre voters bothered to come to the polls because the NDP could possibly win. The 2012 social conservatives did vote again for Wildrose. The 2012 Liberals that voted PC seem to have voted NDP this time as well as some of the people that still voted Liberal in 2012.