People tend to swing to the NDP in large numbers when they are absolutely fed up with both the Liberals and Conservatives. It's partly a protest vote. That happened in Ontario, for instance, when Bob Rae got elected premier. That does not translate into a large sustainable and longterm base of support for the NDP.

Give the Conservatives and/or the Liberals enough rope (time in power) and they will eventually hang themselves. If they succeed in hanging themselves simultaneously, the NDP can benefit greatly and come running up the middle between them.

But it tends to be a short term situation. If the NDP gets into office, the public's anger will soon shift toward them, and their base will shrink back down to a relatively small core of faithful NDP supporters. And then the Liberals or Conservatives will return to their usual primacy.

What really needs to be done is to merge the NDP and the Liberals into a single party. Sadly, though, I can't see it happening. They're both too stuck on their established identities to have the humility to do that. They both fear the loss of their historical identity in the process. Together, they could easily defeat the Conservatives. Apart, they are in a tragically weak position to do so.