Jason presents a reasonable argument. However, I believe he is missing one key element. The party in power does not have the luxury of voluntarily replacing its leaders when that party only has a minority government. As soon as they do so they make the current leader a lame duck completely unable to govern. That in and of itself would be bad enough for the prospects of the Conservatives winning another election. However, there is also the consideration that the government may fall as a result of a no-confidence motion during the chaos of a leadership selection process. Such a threat would make it even more difficult for the party to govern.
So the only way that the Conservatives get rid of Mr. Harper is if he loses the election and even then he may be able to hang on if the Liberals only win a very slim minority. Otherwise Mr. Harper is staying as leader of the Conservative Party. Either as a hero because he manages to pull out a majority government or because they are stuck with him because they cannot risk trying to replace him in a minority government situation.
Of course, if he only has a minority government then he can expect this time to be very different from the last time.
The media will be less inclined to carry his water. One of the reasons why they have been doing so since 2006 is because the corporate bigwigs that run our media believed what their journalist employees were saying. They believed that the Liberals had no hope of forming the government so they could ignore them without having to worry about their interests being threatened. If Mr. Harper only wins a minority the corporate bosses of our MSM will realize that the Liberals will become a government in waiting and it is not in their best corporate interests to alienate said government in waiting. If Mr. Harper only wins a minority government he can expect his long honeymoon with the MSM to be over.
If Mr. Harper only wins a minority government he can expect a very different Conservative Party. Gone will be the days where he will be able to demand that it is his way or the highway. More and more Conservatives, both internal operatives and members of his caucus will be less inclined to stay quiet on issues they consider to be important. Such a scenario could actually be helpful to the Conservatives as it would allow them to shed some of their "secretive" image. However, the weak bench strength of the Conservative caucus and the Conservatives Party's abundance of raving loons could also create the nightmare of giving the Party the image of just being the Reform/Canadian Alliance resurrection.
Then there is the Liberal Party. It will be a true government-in-waiting. It will receive much more attention and positive coverage. It will be a much stronger opposition because of its experience at it for the last couple of years, because of the increased stature of Mr. Dion and because of its considerable bench strength. Of course, if the Liberal Party reacts badly to another Conservative minority and the knives come out for Mr. Dion they will just be shooting themselves in the foot and negating all of the problems Mr. Harper would be facing.
Mr. Harper has to win a majority government. If he only wins a minority government he will be able to hang on to his position as Party leader but he will wish he was somewhere else. If he actually loses this election he will be gone.