The shock departure of a Canadian Cabinet heavyweight has fueled talk about how long Prime Minister Stephen Harper will stay in power, with some in his party predicting he is unlikely to serve a full term if he wins re-election this October.

Harper, 56, who led his right-of-center Conservative Party to victory in early 2006, is seeking to pull off a rare fourth consecutive victory against a stiff opposition challenge.

Numerous party sources say if the Conservatives come first, but fail to secure a majority of seats in the House of Commons elected chamber, Harper's days are numbered. Even if he wins a majority, which polls suggest is out of reach, some top party members expect he will be gone within two years.