Sypher, look at the trend in unemployment over the past two decades. Every time we have a new president, it sky rockets and then slowly goes down over their presidency until once again, we have a new president.
In any case, the Keynesian principle of the fiscal multiplier does play an important role in a democracy. The reason for this is we have periodic policy changes. A government with a single administration--such as totalitarian--for decades upon decades shouldn't base its economic strategy on this principle, granted. However you're neglecting the sway of political direction in America as well as our society's marginal propensity to consume. We're spenders and we need to spend in our economy.
The Keynesian multiplier was never meant for democracy, regardless of political direction. Just look at the failures of the New Deal which caused the 1937 recession and prolonged the Great Depression. Same sway in political direction, same failure. It took total war and the displacement of millions of Americans to bring us out of the Great Depression. Inside and outside lags prevent all stimuli from reaching the designated markets in time, which is why Keynesian fiscal policies have failed every time they've been tried in America.
I will concede that our economy is 70% service oriented and that we are a consumer nation, but Keynesian policies don't remedy the situation. Keynesian stimulus is borrowed from either the citizens or other nations. In either case, we pay interest on those loans, which ends up costing more than what was pumped into the economy in the first place, especially when the amount is vast. Also, if the money is borrowed from the citizens, then it cannot be called a stimulus, but a redistribution because the wealthy (the largest consumers) are taxed to death in order to foot the bill. Find me one example of Keynesian fiscal policy that has worked in America without causing hyperinflation or double digit unemployment. It didn't work under FDR (unemployment never went below 17%). It didn't work under Nixon. It didn't work under Carter, and it didn't clearly didn't work under Bush Jr.