The historic takeover of Fannie Mae and Freddie Mac, which could come as soon as this weekend, moved to the forefront of the presidential campaign Saturday as candidates and congressional leaders seized on the enormous implications for taxpayers and the economy.

John McCain and Barack Obama

Fannie Mae and Freddie Mac together hold or back half of the nation's mortgage debt, and have played an increasingly important role in the real estate market since the credit crisis started in August 2007. A government bailout could cost taxpayers around $25 billion, according to the Congressional Budget Office.