http://faculty.chicagobooth.edu/john.cochrane/research/papers/stimulus_rip.html (I doubt Cochrane is being disingenuous).
Plus there is no example of stimulus working in history. There are too many problems with it:
1) In order to inject money into the economy, the government must first take it out of the economy in another form, debt (in this sense, demand-side tax cuts will not work either if they mean the government must operate on debt)
2) What exactly is the multiplier effect? No one knows, and it may even be negative. If no one knows the actual multiplier (if there even is one), then no one knows how much to spend. How does one measure how much demand has dropped? All of it is using estimates and guesstimates essentially.
3) It takes too much time to get the money out in order to try to stimulate the economy
4) As the money is spent, there can be a lack of accountability in the spending of it
5) People and businesses can respond very negatively to a massive deficit, and thus hold back on their spending and/or hiring, thus the stimulus ends up reducing demand more than increasing it
6) If the government does succeed in creating demand, it can essentially keep the private economy depressed permanantly and prevent it from recovering. The traditional Keynesian idea was that the private economy could not recover without fiscal stimulus from the government. We know that is not true however. If left alone, the private economy will recover on its own and private demand will come back. But if the government steps in long enough and manages to make up for a large amount of that demand, the private-sector may remain permanently depressed, as the government replacing a lot of the lost demand can prevent the private demand from coming back.
This is what some believe happened with Japan. They spent half their GDP in fiscal stimulus, but the net result is that it likely made much of Japanese business dependent on Tokyo
7) The government trying to spend money to stimulate can crowd out private-sector investment, thus hamstringing the economy
8) One of the experiences some European nations have had with attempts at stimulus is inflation. If inflation occurs and drives up the prices of basic goods and services, this can cause consumers to cut back on their spending, thus reducing demand and undermining the very purpose of the stimulus
And so forth.