Democrat Barack Obama was Friday putting the finishing touches to the unveiling of his choice of running mate after unleashing a fusillade of vitriol on White House rival John McCain.
The Republican came under withering fire from Obama after confessing to being in the dark about how many properties he owns, as the pair entered a still-more intense phase of their contest just before the convention season.
Obama returned to his home in Chicago after a week-long tour of southern states, and was to stay huddled with top aides to roll out the closely guarded secret of who his vice presidential pick is.
The Illinois senator told reporters traveling with him in Virginia Thursday: "I've made the selection and that's all you're going to get."
The Democrat's choice of VP nominee will be unveiled at the latest at a campaign event Saturday in the town where Obama first launched his White House bid in February 2007 -- Springfield, Illinois.
Republican McCain was also off the campaign trail Friday, finalizing his own VP pick days before next week's Democratic National Convention in Denver marks the formal start of hostilities for November's presidential election.
While both the candidates will be officially anointed their party nominees over the next fortnight, they have been locked in running battles for weeks already -- and Thursday saw some of the fiercest clashes yet.
Obama ridiculed McCain as being out of touch with everyday Americans in a tempestuous economic period after the Arizona senator, in an interview with Politico.com, could not say how many homes he owns.
"I think -- I'll have my staff get to you," McCain said. "It's condominiums where -- I'll have them get to you."
Aides said he had four houses, but PolitiFact.com said it totaled seven -- the family ranch in Sedona, Arizona and condominiums mostly owned in the name of McCain's wealthy wife Cindy. Politico itself said the number was eight.
"I suppose if you've got seven, maybe eight houses, the economy looks fundamentally sound to you," a fired-up Obama told a capacity crowd of 2,600 at a rally on late Thursday in Chesapeake, southern Virginia.
"But if you're having trouble making the mortgage payment... then the economy looks awful different," he said to roars of approval.
"I make this point not to simply give John McCain a hard time. It's indicative of a different world view about what's happening in America."
The Obama camp put out a television ad called "Seven" mocking McCain's comments to Politico. Ending with a shot of the White House, the narrator said: "Here's one house America can't afford to let John McCain move into."
McCain's campaign battled to limit the damage by pointing to Obama's ties to convicted fraudster Tony Rezko, a Chicago businessman and fundraiser who helped the Democrat with the purchase of his spacious family home.
"One of his 'biggest fundraisers' helped him buy his million-dollar mansion. Purchasing part of the property he couldn't afford," the Republican's team said in its own ad, entitled "Housing Problem."
"Now, he's a convicted felon, facing jail," the announcer intoned. "That's a housing problem."
The row raged as news outlets scrambled for crumbs out of the leak-averse Obama team on his VP pick. The campaign has promised to release the news first to signed-up supporters via cellphone text messages and email.
Obama told USA Today that he had sought out an independent thinker who was ready to be president.
"I won't comment on anything else until I introduce our running mate to the world," he said in an interview posted on the paper's website.
His shortlist reportedly includes Delaware Senator Joseph Biden, Indiana Senator Evan Bayh and Virginia Governor Tim Kaine. Supporters of Obama's former party rival Hillary Clinton are still pushing for her to be on the ticket.
For McCain, leading contenders are said to include former Massachusetts governor Mitt Romney and Minnesota Governor Tim Pawlenty.
The New York Times said General David Petraeus, the commander of US forces in Iraq, had been floated as a "wild-card choice" to join the ticket of Vietnam War veteran McCain.