WASHINGTON — A campaign for the White House long centered on war, energy, and the economy has shifted to a fight over the candidates’ personal fortunes.

The presidential race took a sharply negative turn yesterday as the Obama campaign launched a multipronged attack on Mr. McCain after the presumptive Republican nominee appeared to forget how many homes his family owns. In response, the McCain campaign unleashed its file on Antoin Rezko, the convicted Chicago developer who helped Mr. Obama find the $1.65 million mansion he bought.

The back-and-forth taunts and dueling campaign ads played out on the eve of the Democratic National Convention and underscored the extent to which each candidate is trying to paint the other as out of touch with the concerns of middle-class Americans. Republicans have labeled Mr. Obama a “celebrity” and likened him to pop stars, while Democrats have criticized Mr. McCain as insensitive to the nation’s economic woes. Democrats seized on the Arizona senator’s response when he was asked at a forum last week how much money defined a person who is rich, and he initially replied: $5 million.

The offensive from the Obama campaign is part of a newly confrontational strategy in the days leading up to next week’s convention as polls nationally and in battleground states show his lead over Mr. McCain evaporating.

In an interview with Politico published early yesterday, Mr. McCain was asked how many houses he owned. He hesitated. “I think — I’ll have my staff get to you,” he replied. “It’s condominiums where — I’ll have them get to you.”

His aides told the newspaper he and his wife Cindy owned at least four, in Arizona, California, and Virginia. Politico later reported the total was eight, and all were in the name of Mrs. McCain, the heiress to a beer distribution company, along with their children, trusts, and companies they own.

The Democrats, citing their own search of property records, settled on seven worth $13 million, and they pounced quickly.

Mr. Obama skewered his rival at a campaign stop in Virginia, disputing his assertion recently that the fundamentals of the American economy are “strong.”

“I guess if you think that being rich means you’ve got to make $5 million and if you don’t know how many houses you have, then it’s not surprising that you might think the economy was fundamentally strong,” Mr. Obama said. “But if you’re like me, and you’ve got one house, or you are like the millions of people who are struggling right now to keep up with their mortgage so they don’t lose their home, you might have a different perspective.”

He continued: “So there’s just a fundamental gap of understanding between John McCain’s world and what people are going through every single day here in America.”

Shortly after Mr. Obama spoke, his campaign announced that surrogates would be holding events in 16 states to attack Mr. McCain over his remark. Simultaneously, it released a hastily crafted television ad in which a narrator says Mr. McCain “lost track” and “couldn’t remember” how many homes he owned. It concluded with an image of the White House. “And here’s one house the American people can’t afford to let John McCain move into,” the narrator intones.

The McCain campaign responded sharply, with a spokesman suggesting Mr. Obama was in no position to play populist. “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?” the spokesman, Brian Rogers, said. “Does a guy who worries about the price of arugula and thinks regular people ‘cling’ to guns and religion in the face of economic hardship really want to have a debate about who’s in touch with regular Americans?”

Late yesterday, the McCain campaign released a TV ad explicitly tying Mr. Obama to Rezko, a longtime friend and donor who was convicted in June on 16 counts of corruption-related felonies. He is to be sentenced in October. Mr. Obama was not implicated in any criminal activity, but he has said it was a mistake for him to partner with Rezko in buying adjacent properties on the same day in a wealthy Chicago neighborhood while it was publicly known that Rezko was under federal investigation for soliciting kickbacks.

The ad, which includes the image of a jail cell, implies that Mr. Obama provided political favors to Rezko by supporting his bid for state grants to build housing projects in his district.