@coldjoint,
Pardos is not correct. The original question was fairly clearly about the net economic effect of Federal spending: i.e. whether the net economic effect of Federal spending involved a positive effect on job creation. This is a popular theme lately pursued by those who argue for consumer demand as the leading economic driver in these things. It is certainly a factor, but only one of several in a very complex and not fully understood process about which economists argue incessantly.
In any event it is fairly obvious that Federal tax collections reduce potential consumer demand by the amount of tax collected. If that money is in turn used in domestic Federal spending the demand is replaced, at best, on a dollar for dollar basis, s
o the net effect is zero.
Parados also argued that if the money is "invested" in roads or other like infrastructure then the beneficial effect can be greater than in , for example, merely creating more useless drones working for the government. In that he is certainly correct. Economists call this the investment multiplier. However, because the private sector is generally more efficient in its investment spending and more focused on the economic returns involved the effect for private sector investment is generally greater.
If increased Federal spending is funded by additional debt, then an additional factor enters the picture. That is the more or less permanent drag on the economy of interest payments on the debt and a generally upward pressure on interest rates caused by this increased demand for investment dollars by the government, thereby raising the cost of almost all investment public or private. The effects of this are hard to estimate, but all negative.
Temporary boosts to economic activity can indeed be attained by deficit spending, but this game has its very finite limiteds as the Greeks discovered a few years ago and the French are finding out now.