When the federal government runs a deficit—that is, spends more than it collects in revenue—it borrows money to cover the difference, usually by issuing IOUs in the form of U.S. Treasury securities. The debt ceiling is a legal limit on the amount of borrowing the Treasury can do. Before 1917, each loan issued by the Treasury required authorization from Congress. When the U.S. entered World War I, however, Congress changed the law to allow the Treasury to sell war bonds (Liberty Bonds) as needed, provided that bond sales didn’t exceed a specific amount—the debt limit. Over the last three decades, the limit has precipitated political battles during which some legislators have used the vote on the debt ceiling to try to slow the growth of federal spending […]