Later, the McCain campaign told Politico that McCain and his wife, Cindy, have at least four in three states - Arizona, California and Virginia.
Property records reviewed by The Associated Press show McCain and his family appear to own at least eight homes: A ranch and two condos in Arizona; three condos in Coronado, Calif.; a condo in La Jolla, Calif.; and another in Arlington, Va. The number of houses is a bit trickier to determine since the ranch has at least four houses and a two-story cabin on it.
Last week McCain cracked that being rich in the U.S. meant earning at least $5 million a year. His latest comments gave Democrats an opportunity to suggest that McCain cannot relate to ordinary voters.
Campaigning in Chester, Va., Obama said: "I guess if you think being rich means you've got to make $5 million and if you don't know how many houses you have, it's not surprising you might think the economy is fundamentally strong." He returned to the McCain remark later, saying of teachers: "Most teachers hold themselves accountable. They didn't go into teaching to make money. They don't have seven houses."
The Obama campaign also announced 16 campaign events across the country to highlight the comment and try to turn the tables on McCain's effort to cast him as an elitist. In the battleground state of Michigan, Obama's campaign asked volunteers to guess how many houses McCain owns, a contest dubbed, "Who Wants to Be a Millionaire: McCain Edition."
While both sides are trying cast the other as too rich to understand the working class, the truth is neither candidate is hurting for money.
McCain's tax returns showed a total income of $405,409 in 2007. According to her 2006 tax returns, Cindy McCain had a total income of $6 million. Her wealth is estimated by some at $100 million, based on her late father's Arizona beer distributorship. She has not released her 2007 returns, which she files separately from her husband.
Obama and his wife, Michelle, reported making $4.2 million in 2007.
In the 2004 campaign, Republicans tried to use wealth against Kerry even though President Bush and Vice President Dick Cheney were multimillionaires themselves. In 2005, Kerry reported a net worth between $165 million and $235 million, most of it controlled by his wife, Teresa Heinz Kerry.
Underscoring how seriously the McCain campaign takes the house controversy, the Republican National Committee responded with a Web site highlighting Obama's ties to Chicago businessman Antonin "Tony" Rezko, a friend and contributor who was convicted in June on more than a dozen felonies in a corruption scandal.
Obama and his wife bought their home in Chicago in 2005 for $1.6 million after getting advice from Rezko. The corruption case had no connection to Obama, and Obama has said it was a mistake to work with Rezko on buying the house.
"Does a guy who made more than $4 million last year, just got back from vacation on a private beach in Hawaii and bought his own million-dollar mansion with the help of a convicted felon really want to get into a debate about houses?" asked McCain campaign spokesman Brian Rogers.
However, the campaign got one thing wrong: Hawaii has no private beaches. Obama, who was born in Hawaii and spent most of his youth there, visited relatives during a recent vacation and joined the public swimming and surfing in the ocean.
In a forum last week with the Rev. Rick Warren, McCain was asked to define the word "rich" and to give a figure. After promoting his tax policies, McCain said: "I think if you are just talking about income, how about $5 million?" The audience laughed, and he added: "But seriously, I don't think you can - I don't think seriously that - the point is that I'm trying to make here, seriously - and I'm sure that comment will be distorted - but the point is that we want to keep people's taxes low and increase revenues."
Asked the same question at the forum, Obama said those making $250,000 and higher are in the top 3 to 4 percent and "doing well."