Stephen Harper has signalled that he won't be calling an election because of the likelihood of another minority government:

"We're entering a period of minority government. We've had a couple in a row now," he said Wednesday.

Harper said with four political parties securing a minimum of 20 seats each, it would be difficult for any side to win a majority government.

"I think the possibility of a minority government in a subsequent election is pretty high," he said. "At the same time, I don't think Canadians want an election and the government is not seeking an election."

Harper is right that we are in a period of minority governments, but he is wrong about the root cause.  The situation of having four parties in a situation to win 20 seats has been the case ever since the Bloc was formed in 1991.  However, the new dynamic in play is that the Greens have built up our core level of support to 10% and this level of support is not going away.  Once voters switch to the Greens they don't go back to the older parties.

This 10% level of support has made it all but impossible for the Conservatives or Liberals to get into what has traditionally been considered comfortable majority territory of 40% or more in the polls.  Consider that in the past those two parties typically shared about 75% of the vote, with a floor of around 30%.  So one party could be at 40% in the polls and the other could be at 35%, or one could be at 43% and the other could be at 32%.  The proper timing of an election call in the latter situation could easily win a majority, and this situation often presented itself.

But now the Greens have pulled about 5% of their support from those two parties, so they only share about 70% or less support between them.  That means that for one party to get to (say) 43% in the polls the other party would have to be at 27%.  And that lower level is unlikely to occur.

The Conservatives and Liberals have both flirted with 40% support in recent years but they can't maintain it since it means the other party is hovering at a historical low of around 30%.  So it is difficult for their leadership to come up with a scenario where they can win a majority using traditional benchmarks. 

As it happens, the new benchmark for a majority is probably around 36% since the 10% of Green Party votes are not really in play. The breadth of our support means that there is no guarantee that the Greens will win even a single seat.  So 308 seats are in play between 90% of the voters voting for the other four major parties (e.g. 90% x 40% = 36%).  But it will be far harder for the Liberals or Conservatives to predict if they can win a majority at 36% or 37% (even if it might occur in practice), which is why Harper is hesitating to pull the trigger on an election.

One of the complaints against using proportional representation in our federal elections is that it will trigger the end of majority governments.  But Green supporters have already triggered this situation, perhaps permanently, even without winning a seat.  This is just one more example of how the current electoral system is broken and has to change.