The sale suggests not only that the bond markets are healthy again, but also that the quasi-government agency is succeeding in its efforts to become a benchmark security in those markets.

This sale was made despite increasing scrutiny from politicians and banks that say the government-sponsored Fannie Mae and Freddie Mac have advantages that let them unfairly compete with private businesses. Other critics say the growth of these agencies could put their investors at risk, and call for new limits on them. Rep. Richard Baker, a Louisiana Republican, introduced a bill that would give Fannie Mae a new regulator and prevent it from borrowing directly from the Treasury, a move that would weaken Fannie's credit quality in the bond markets.

Although the political pressure has lessened since spring, Fannie Mae still had to pay better terms to lure investors. "It's a quarter point more than before the Baker bill," says Arthur Frank, director of fixed income research at Nomura Securities International Inc. in New York. Fannie Mae began with a spread of about 80 points over the 10-year Treasury bonds at the end of February. This widened to 124 basis points in mid-May, before closing the deal this week with a spread of 106.5 basis points.