The concept that giving the middle-class more money to buy things seems to not be well known in either party, as both of their plans to start the economy make bad assumptions.
Democrats: Keynesian stimulus designed to jump start the economy assuming it will be enough for the public to start buying things and hiring workers.
Republicans: Tax cuts so business can hire more people.
The Democrats' stimulus won't work because the middle class has less income than before meaning they can't/shouldn't be buying things to stimulate the economy. The Republicans' tax cuts won't work because businesses won't hire people unless sales go up. Sales won't go up because the middle class has less income than before.