The union representing the nation's letter carriers has hired a former Obama administration adviser as it faces proposals that could lead to layoffs of thousands of its members. Ron Bloom oversaw the administration's auto industry task force. His hiring by the National Association of Letter Carriers comes as the union is negotiating a new contract with the U.S. Postal Service, which cannot find a way to make delivering mail by hand profitable. It is losing billions of dollars and is considering drastic steps to cut costs.