WASHINGTON—Democrats and Republicans queasy about a federal rescue of mortgage giants Fannie Mae and Freddie Mac are coalescing around the idea of letting the government slap limits on the multimillion-dollar pay packages of their executives.

Key lawmakers—puzzling over how to explain to constituents why they voted to bail out the troubled government-sponsored firms—see new curbs on compensation for the top officers as a crucial measure to cut down on the cringe factor.

At a time when Fannie Mae’s and Freddie Mac’s troubles have investors worried and the government ready to jump in with untold sums of cash, the lavish pay of the two companies’ executives is increasingly difficult to defend, they say.

Sen. Bob Casey, D-Pa., says Fannie and Freddie “have had their hard-won credibility undermined in recent weeks,” on the heels of major accounting scandals at the firms in 2003 and 2004.

“While the subprime mortgage crisis is hardly the fault of these companies, past practices of awarding huge bonuses and higher executive salaries calls into question the prudence of extending an unlimited credit line of taxpayer money to the companies whose management practices have been questionable over recent years,” Casey said in a letter to Treasury Secretary Henry M. Paulson.