Political Staples

What she said.

...the Liberal and New Democratic parties are very different entities. And it wasn't so much a union as a reunification for the right after the 1987 schism caused by the founding of the Reform Party.
While Western conservatives felt alienated from their eastern brethren, ideologically they were not that far apart. They'd all been one big happy family. OK, scratch the happy bit. They were once a big fractious family.
Yet it took years to heal the wounds that separated them.
How, then, can two parties with such different histories and such disparate philosophies as the NDP and the Liberals ever find common ground?

I can add one more point. A reunification of the Reform/Alliance and Progressive Conservatives only happened when both sides concluded that they would never form a government separate and could only challenge the Liberals as a united party. Do any Liberals think they will never form a government again? Answer that question and you have your answer about whether or not there will a merger between the Liberals and NDP. Well, that and the NDP would have to start caring that they will never form a government. Yeah, the odds aren't very good.