Sens. Mark Warner, D-VA, and Bob Corker, R-TN, are working on legislation that would create a new federal mortgage guarantor, replacing Fannie Mae and Freddie Mac, according to trade and legislative officials familiar with the matter. However, as Inside The GSEs went to press this week, little was known in terms of specifics. This would be a federal insurance entity, involving insurance wraps said one trade group official. It would involve a tiered risk-sharing system.