Canadian Politics Today

GST isn't an entity of its own, for government to collect it, people need to have money to buy stuff.
If GDP is contracting, what are you going to tax?

Well obviously you're not going to raise taxes now.  But maybe when the recession ends they may have to.  But voters dislike taxes more than they dislike debt because, well, they like having their cake and eating it too.  People are generally irresponsible shmucks.  So the government will have pressure not to raise taxes.  Meanwhile they get to play the hero by spending other people's money, which will benefit them in the inevitable election.