The government-sponsored enterprises’ new low downpayment programs received a vigorous defense from Melvin Watt, the director of the Federal Housing Finance Agency, at a hearing this week by the House Financial Services Committee. Republicans on the committee attacked the programs from a number of angles, including raising concerns about default rates on mortgages with lower downpayments and fears of a “race to the bottom” with the FHA. “If you carefully look at other considerations and take them into account in deciding whether to back that credit, you can ensure...