Quoted from the Globe and Mail (full article here):

There has never been alternation in office in Alberta, unlike in several other provinces where the Liberals and Conservatives take turns governing. In Alberta, one party governs for a long stretch (36 years for Social Credit, 39 and counting for the Conservatives), then is obliterated by a new party without governing experience.

Quoted from Fort McMurray Today (full article here):

"We are in a time of political transition provincially here in Alberta," Manning told the 120 or so in attendance. Albertans are going to have to decide if they think the government can renew and reinvigorate itself to provide leadership for the future, or do they think one of these opposition parties... can make the transition to a governing party."

Quoted from CBC Edmonton (full article here):

"In particular, I saw that the policies that were coming out of the Alberta government were too left and were inconsistent with my own personal conservative values and beliefs," Saskiw told CBC News. Saskiw said he was unhappy with the increase in government spending in the last budget and the way policy suggestions from grassroots members of the party were not incorporated into government decision-making.