In general terms, we've known since Keynes wrote about the Great Depression in the 1930s that monetary and fiscal policy have their moments when they have their greatest impact. Monetary policy has its least impact as interest rates get close to the lower bound, which is to say people have already borrowed to buy homes or to buy cars, companies have borrowed to do investments, and so on. Lowering interest rates a little further has only a marginal impact on the side.
It is in that context, when we're in that neighbourhood, that fiscal policy has the largest impact of all the possibilities one could contemplate. The reason is simply that when we have models of the economy, and we simulate fiscal policies, normally we start from a position of equilibrium. We are far below Canada's equilibrium at this time. We have plenty of excess capacity.
In this context, there are no other movements anticipated, such as interest rates or exchange rates, that would partially offset a fiscal change. It's in that sense that it has more power for the amount of fiscal action one takes than monetary policy has in this setting.