“Mankiw’s first-year economics textbook draws the demand for money as a downward-sloping demand curve, and (to simplify his argument) the supply of money as a vertical line—meaning that it is fixed. He then explains that an increase in government spending means that the government borrows some of this fixed supply, making less available for the private sector. ..
Per #MMT gov debt are private wealth. It is wealth unlike bank lending which zeros out.