I hope the great 'coalition' bogeyman will vanish from the election campaign soon. However my guess is that Harper will continue to push it. Unfortunately, I think the public is just not fully informed, and Harper's rhetoric is serving his partisan needs, negatively affecting public understanding.
In what follows, I hope to clarify what I believe public understanding should be. This is the third in my series of election posts, the others being here and here.
If a party has a majority, it is the end of the story. Let's call that Scenario 1. The polls suggest it is unlikely, although it is essential for the main parties to campaign assuming this will happen, lest they appear weak.
In a minority situation, let's get one thing straight: it is clear that the party that gets the most seats would be asked to try to form a government. That is likely to be the Conservatives, but could be the Liberals if they do well in the campaign. However in a minority situation, there are several scenarios from that point forward. In what follows I will assume the minority government continues to be led by the Conservatives, even though I hope not.
Scenario 2 is that the minority party governs for a considerable period of time by being co-operative with one or more the other parties. This is how Harper should have been governing. However instead of co-operating, which implies regularly sitting down with the opposition and negotiating policies that are acceptable to multiple parties, he relies on the 'fear of an election' to bully other parties to vote with him. I will call a repeat of this outcome Scenario 2a. If, after the current election, Harper is extremely close to a majority, then it would be principled (to use Igantieff's own term) for Ignatieff to support the government in the way he has, at least for a few months. I think, however, that Ignatieff and the Liberals simply cannot allow this to happen again for more than a few months. Doing so would destroy the credibility of the Liberals, and would continue to show Ignatieff as a weak leader. The Liberals would need to lay down a set of policies that they feel are critical, and demand negotiations. The NDP could do the same. Scenario 2b is that the Conservatives actually listen, and a minority government functions in the way it is supposed to. Knowing Harper, this seems unlikely, but Ignatieff could perhaps force it with careful tactics.
Scenario 3 is the formation of a coalition. This could happen immediately after an election (Scenario 3a), as happened in the UK, with the party that has the most seats joining with the third- or fourth-place party. A coalition can be quite stable, despite Harper's protestations about his. Stability depends on party discipline, just as when when a single party governs. Coalitions tend to be most unstable when they rely on support of parties with regional or special agendas, as could be the case in Canada if a coalition involved the Bloc.
Scenario 3b is that a minority government (Scenario 2) is defeated fairly early in their mandate, and another party is asked to try to form a government without an election intervening, and with a coalition being the most sensible outcome. This is what almost happened a couple of years ago, and was thwarted by Harper proroguing Parliament.
I think a replay of Scenario 3b is the most likely outcome given the current polls. Harper's political agenda is to prevent this by forcing Ignatieff to categorically state that he will not form one, as he has done, and then blast him as a 'once again, a liar' afterwards. However, from my perspective, it would still be principled for Ignatieff to form a coalition if the Conservatives do not co-operate as in Scenario 2a. The question will be: Would Harper be able to play the same proroguing trick? Perhaps. Therefore, Ignatieff would have to force the government to co-operate or else defeat it even earlier than last time.
Ignatieff has now promised not to form a coalition. That is fine. It was his only sensible course of action. Saying that he might do it would simply have resulted in strategic voting, with people opting for the NDP, surmising that the NDP would then have a greater chance of gaining power. The result would have been vote splitting, and the Conservatives getting more seats.
However, Ignatieff has a 'bogeyman' card that he should play. He should insist on an answer to the question, in the case the Conservatives get a minority, will they negotiate and work with the opposition or insist on acting as though they have a majority? He can claim that he will do exactly this if he gets a minority, and lambaste the Conservatives for being 'parliamentary obstructionists'. He also should promise that 'enough is enough,' in the case of a minority he will not support Conservative bills any more unless they incorporate enough properly negotiated measures to satisfy the opposition. I don't think it would be politically bad for Ignatieff to talk about the possibility of him getting another minority. In fact if is is plain about this, he can then say, vote Liberal if you want to avoid another election soon, since "we all know the Conservatives are parliamentary obstructionists, and we won't put up with that any more, period".
A couple more points: Harper is playing the "unstable" bogeyman. Frankly, a coalition ought naturally more stable than a minority.
Harper is also playing the "election hurts the economy" bogeyman. That is nonsense. Lack of stability can hurt the economy by not allowing budgets to pass and leaving investors uncertain about policy direction. However, three years is the historical record survival time in Canada for a minority, so Harper is being very arrogant to expect that he could manage to bully-govern much longer. An election now, followed by a majority (Scenario 1), a co-operative minority (Scenario 2) or a coalition (Scenario 3) should in fact be the most stable option for the coming 3-4 year period.