Keynesian economics is the perpetual motion machine of the left. You build a model that assumes government spending is good for the economy and you assume that there are zero costs when the government diverts money from the private sector.
With that type of model, you then automatically generate predictions that bigger government will “stimulate’ growth and create jobs. Heck, sometimes you even admit that you don’t look at real world numbers.
This perhaps explains why Keynesian economics has a long track record of failure. It didn’t work for Hoover and Roosevelt in the 1930s. It didn’t work for Nixon, Ford, and Carter in the 1970s. It didn’t work for Japan in the 1990s. And it hasn’t worked this century for either Bush or Obama.