PHOENIX  When Senator John McCain is in Washington, he lives in a luxury high-rise condominium in Arlington, Va., owned by his wife, Cindy Hensley McCain. Mrs. McCain also owns their condos in Phoenix, San Diego and Coronado, Calif., and their vacation compound near Sedona, Ariz. And it is the beer business, Hensley & Company, she inherited from her father that is the source of the McCain family fortune.

That fortune makes Mr. McCain one of the richest members of the Senate. Yet barely a sliver of it is in his name.

Democrats have increasingly highlighted Mr. McCain’s wealth. Senator Barack Obama ridiculed him on Thursday for being unable to say how many homes he owned, saying it showed that Mr. McCain was out of touch with ordinary Americans. But with the McCains’ money in Cindy McCain’s name, as dictated by a prenuptial agreement, the senator’s finances are more difficult to assess and scrutinize than those of many other political candidates.

The husbands and wives of senators are subject to fewer disclosure requirements than their office-holding spouses. In addition, Mrs. McCain, who files separate tax returns from her husband, controls a privately held company and invests mainly through a web of limited-liability corporations and trusts that have few disclosure requirements. She declined to be interviewed.