To understand why increased government spending is unlikely to lead to economic prosperity, just apply common sense. Recognize that when the federal government desires to spend more, the funds it needs must come from one of three sources: increased taxes, increased borrowing, or printing more money.
When taxes are increased, the government takes money from private entities and spends it according to its own priorities, but there is no “net” stimulus. When funds are borrowed, they must eventually be repaid, with interest — thus any stimulus effect will be short-lived. Finally, printing more money can produce an immediate economic stimulus, but once again the benefit will be only temporary. All else being equal, printing more money cheapens the value of the dollar and causes future inflation, which can quickly decimate the lower and middle-income classes.