Incensed by the advertisements, several current and former executives of the companies came forward to discuss the role that Rick Davis, Mr. McCain’s campaign manager and longtime adviser, played in helping Fannie Mae and Freddie Mac beat back regulatory challenges when he served as president of their advocacy group, the Homeownership Alliance, formed in the summer of 2000. Some who came forward were Democrats, but Republicans, speaking on the condition of anonymity, confirmed their descriptions.

“The value that he brought to the relationship was the closeness to Senator McCain and the possibility that Senator McCain was going to run for president again,” said Robert McCarson, a former spokesman for Fannie Mae, who said that while he worked there from 2000 to 2002, Fannie Mae and Freddie Mac together paid Mr. Davis’s firm $35,000 a month. Mr. Davis “didn’t really do anything,” Mr. McCarson, a Democrat, said.

Democratic vice presidential candidate Joe Biden said Republican John McCain protected offshore tax shelters worth billions of dollars to U.S. insurance giants.

In his second trip in four days to this battleground state Tuesday, Biden said McCain promised to oppose any efforts to close a "Bermuda loophole" where American companies shielded $4 billion to $7 billion from U.S. taxes.

By claiming their headquarters as Bermuda, Biden said, firms actually based in the United States can keep profits out of the reach of the Internal Revenue Service.

"They're skipping out on billions of dollars in taxes, and that money could be used to insure our children, ... to make sure the (Veterans Administration) is not underfunded, to rebuild bridges that are crumbling around the nation," Biden said.

Biden was referring to a provision of tax law that some insurance companies can use to wipe out much of their U.S. tax liability. The companies that issue fire, property and casualty insurance are allowed to establish a Bermuda office and transfer the premiums they collect there, treating them as business expenses. That creates a deduction that erases millions of dollars in taxable profits, costing the U.S. Treasury $4 billion or more a year.

McCain spent three days in Bermuda in August 2007 meeting business and political leaders, and while there was quoted by the island's main newspaper, the Royal Gazette, as promising to defend tax breaks for insurance companies that locate there.

"The industry, the reinsurance that's had such phenomenal success has been good for both nations," McCain was quoted as saying in an Aug. 23, 2007 article. "I would oppose any measures that would upset that."