Republican Sen. Bob Corker this week introduced legislation that would wind down Fannie Mae and Freddie Mac in part by limiting their new MBS issuance to a declining share of total new mortgage securitization. The Tennessee lawmaker’s Residential Mortgage Market Privatization and Standardization Act would “responsibly unwind” the government-sponsored enterprises by gradually reducing their portfolios of guaranteed mortgage-related assets while taking steps to bring uniformity and transparency to the housing market so that private capital can begin to replace the GSEs. The Corker bill would annually reduce the...