Because two disparate clients demand loyalty from Fannie Mae and Freddie Mac, these government-sponsored entities must fulfill two ultimately irreconcilable roles.

The future of Fannie Mae and Freddie Mac is becoming cloudier. Legislation in Congress and a clear lack of support at the Treasury are harbingers of political difficulties ahead. Perhaps more important is the fact that these two government-sponsored enterprises (GSEs) are growing faster than the housing market. By...