Luckily, We Have Hindsight
When Franklin Roosevelt came into office, he took over the presidency from a man who watched as the nation's economy collapsed around him. Roosevelt determined that in order to reinvigorate that economy, the Federal government had to spend money to stimulate it.
He was right, and his programs brought about improvement. Under pressure from the anti-stimulators, however, Federal spending was eased under the impression that the moneys spent had been sufficient. They were not, and the economy began to slump again, not to be truly repaired until World War II -- the Great Stimulus.
Thankfully, we have the hindsight to have observed Roosevelt's stumble and not repeat it. Unless, as so many would have us do, we keep our eyes tightly shut.