Then came Lyndon B. Johnson’s “guns and butter” excesses, which were intensified over one perfidious weekend at Camp David, Md., in 1971, when Richard M. Nixon essentially defaulted on the nation’s debt obligations by finally ending the convertibility of gold to the dollar. That one act — arguably a sin graver than Watergate — meant the end of national financial discipline and the start of a four-decade spree during which we have lived high on the hog, running a cumulative $8 trillion current-account deficit. In effect, America underwent an internal leveraged buyout, raising our ratio of total debt (public and private) to economic output to about 3.6 from its historic level of about 1.6. Hence the $30 trillion in excess debt (more than half the total debt, $56 trillion) that hangs over the American economy today.

This explosion of borrowing was the stepchild of the floating-money contraption deposited in the Nixon White House by Milton Friedman, the supposed hero of free-market economics who in fact sowed the seed for a never-ending expansion of the money supply. The Fed, which celebrates its centenary this year, fueled a roaring inflation in goods and commodities during the 1970s that was brought under control only by the iron resolve of Paul A. Volcker, its chairman from 1979 to 1987.

Under his successor, the lapsed hero Alan Greenspan, the Fed dropped Friedman’s penurious rules for monetary expansion, keeping interest rates too low for too long and flooding Wall Street with freshly minted cash. What became known as the “Greenspan put” — the implicit assumption that the Fed would step in if asset prices dropped, as they did after the 1987 stock-market crash — was reinforced by the Fed’s unforgivable 1998 bailout of the hedge fund Long-Term Capital Management.

That Mr. Greenspan’s loose monetary policies didn’t set off inflation was only because domestic prices for goods and labor were crushed by the huge flow of imports from the factories of Asia. By offshoring America’s tradable-goods sector, the Fed kept the Consumer Price Index contained, but also permitted the excess liquidity to foster a roaring inflation in financial assets. Mr. Greenspan’s pandering incited the greatest equity boom in history, with the stock market rising fivefold between the 1987 crash and the 2000 dot-com bust.

Soon Americans stopped saving and consumed everything they earned and all they could borrow. The Asians, burned by their own 1997 financial crisis, were happy to oblige us. They — China and Japan above all — accumulated huge dollar reserves, transforming their central banks into a string of monetary roach motels where sovereign debt goes in but never comes out. We’ve been living on borrowed time — and spending Asians’ borrowed dimes.

This dynamic reinforced the Reaganite shibboleth that “deficits don’t matter” and the fact that nearly $5 trillion of the nation’s $12 trillion in “publicly held” debt is actually sequestered in the vaults of central banks. The destruction of fiscal rectitude under Ronald Reagan — one reason I resigned as his budget chief in 1985 — was the greatest of his many dramatic acts. It created a template for the Republicans’ utter abandonment of the balanced-budget policies of Calvin Coolidge and allowed George W. Bush to dive into the deep end, bankrupting the nation through two misbegotten and unfinanced wars, a giant expansion of Medicare and a tax-cutting spree for the wealthy that turned K Street lobbyists into the de facto office of national tax policy. In effect, the G.O.P. embraced Keynesianism — for the wealthy.

The explosion of the housing market, abetted by phony credit ratings, securitization shenanigans and willful malpractice by mortgage lenders, originators and brokers, has been well documented. Less known is the balance-sheet explosion among the top 10 Wall Street banks during the eight years ending in 2008. Though their tiny sliver of equity capital hardly grew, their dependence on unstable “hot money” soared as the regulatory harness the Glass-Steagall Act had wisely imposed during the Depression was totally dismantled.