WASHINGTON (AP) — For years, mortgage giants Fannie Mae and Freddie Mac tenaciously worked to nurture, and then protect, their financial empires by invoking the political sacred cow of homeownership and fielding an army of lobbyists, power brokers and political contributors.

New attention is being focused on the bruised mortgage companies as the Bush administration presses its rescue plan to Congress. Some lawmakers have challenged the plan’s open-ended nature and expressed fears of a potential big taxpayer bailout in an election year.

Over the past decade, both Fannie and Freddie made the list of Washington’s top 20 lobbying spenders. They spent a combined $170 million to cultivate allies during that period, a bit less than the American Medical Association and a bit more than General Electric. At the same time, their executives have consistently led the mortgage-banking sector in campaign giving to members of Congress, contributing a combined $16.2 million since 1997.

People who have lobbied on their behalf have played or are playing roles in the presidential campaigns of both Republican John McCain and Democrat Barack Obama.

Defenders, including President Bush and Treasury Secretary Henry Paulson, say the nation’s two major mortgage companies — which own or guarantee roughly half of the nation’s $12 trillion in outstanding mortgage debt — are more vital than ever to the smooth functioning of the nation’s jittery financial markets.