(CNN) - John McCain and wife Cindy do not file joint tax returns, and the campaign said Friday they will not release her 2006 and 2007 tax returns along with the candidate's.
The campaign argues that the two keep their finances separate, and that she has privacy concerns for her kids.
The Obamas and the Clintons both file taxes jointly.
Some of Cindy McCain's financial statements have been released as part of regular Senate disclosures.
The McCain campaign notes John Kerry's wife, Teresa Heinz, did not release her complete tax returns during the 2004 campaign.
An heiress to her father's stake in Hensley & Co. of Phoenix, Cindy McCain's worth has been estimated to be around $100 million.