They vowed a nonstop, two-month offensive to make up for any lost ground as Kerry made personnel changes at the top of his campaign for the final sprint to Election Day.
Bush campaigned Sunday in battleground West Virginia, telling supporters a Democratic administration would "stifle job creation" with tax increases.
Both campaigns forged ahead without waiting for the traditional Labor Day kickoff, sparring over the tone of the contest, two wars 30 years apart and the president's domestic performance.
"After a week of relentless negativity, we will be fighting back using Bush's own record on the economy, jobs and health care," Democratic Party chief Terry McAuliffe said in a conference call with reporters.
Although payroll jobs have grown by 1.7 million in the last 12 months, the economy still has lost 913,000 jobs overall since Bush took office.
Both sides said the race probably would tighten after several national polls over the weekend showed Bush opening a 10-point or larger lead.
"The thing about a bounce is, it goes up and then it comes down," said Kerry's campaign manager, Mary Beth Cahill.
"At the end of the day, this is going to be a very, very tight race," said Bush re-election chairman Marc Racicot. Both were interviewed on CBS' "Face the Nation."
With many Democrats outside the Kerry term urging the candidate to take steps to reinvigorate his campaign, Kerry has moved John Sasso, a longtime adviser and Boston operative who once ran the presidential campaign of Michael Dukakis, from the Democratic National Committee to a top spot inside his campaign.
Sasso will be a senior adviser traveling with Kerry through Nov. 2. Replacing him as liaison to the DNC will be Michael Whouley, who helped Kerry win the Iowa caucuses.
The changes put three Boston operatives in charge of his campaign: Cahill, Sasso and Whouley.
Kerry was reunited with his wife Teresa Heinz Kerry at their home in Pittsburgh on Sunday. She was treated in an Iowa hospital late Saturday after complaining of an upset stomach.
Bush told a rally in Parkersburg, W.Va., "This Labor Day weekend, it is important for American workers to know that my opponent wants to tax your jobs."
Kerry has said he would restore taxes to pre-Bush levels only for people earning more than $200,000, and would cut them for middle- and low-income earners.
Bush won the state by 6 percentage points in 2000, and polls show him again holding a lead, even though Democrats wield a 2-1 advantage in voter registration.
Some Democrats have complained that Kerry waited too long before fully responding to attacks on his military service in Vietnam, especially after making his war experience central to the Democratic convention five weeks ago.
A group calling itself Swift Boat Veterans for Truth (search) has accused Kerry in ads, speeches and interviews of lying about his Navy combat experience.
Cahill defended the timing of the campaign's response. "These were baseless lies. We answered it on our own time. And we were backed up by the facts," she said.
McAuliffe told reporters Democrats would seek to counter "four days of mean vicious attacks" from Republicans.
"I'm not concerned about the polls. They've just finished up their convention," McAuliffe said. He said Kerry was doing well in some battleground states Bush carried in 2000, mentioning Florida, Ohio and New Hampshire.
Meanwhile, six in 10 Americans called economic conditions poor or only fair, while 32 percent called conditions good or excellent, according to a new Time magazine poll.
The poll showed Americans evenly split on Bush's handling of the economy, with 49 percent approving and 48 percent disapproving. However, 57 percent said they felt they had not personally benefited from his tax cuts.
Retiring Sen. Bob Graham, D-Fla., one of several fellow Democrats to raise questions about Kerry's campaign performance, defended describing him as still a little "out of focus" for many voters.
Asked on NBC's "Meet the Press" if Kerry should be clearer on what he would do in Iraq (search), Graham said, "I would suggest he also needs to say that the issue is now beyond Iraq; it is now Iran, it is now North Korea."
Ken Mehlman, Bush's campaign manager, wouldn't be pinned down on a schedule for debates. Kerry has said he'll be in Coral Gables, Fla., on Sept. 30 for the first of three presidential debates proposed by the Commission on Presidential Debates.
"We look forward to these debates. We look forward to having a debate about debates. We will, in an appropriate time, which is shortly, talk about our intended participation," Mehlman told ABC's "This Week."
Kerry spokesman Joe Lockhart, appearing on the same program, shot back: "Debates don't need to be debated. We don't need 'intended.' If the president has an agenda that he can defend, show up at the debates."
Democrats said the agenda Bush outlined in his convention speech for a second term -- including private Social Security (search) investment accounts and tax-free health and retirement plans -- would push the nearly $400 billion federal deficit further in the red.
Republican Sen. John McCain of Arizona agreed, and said Bush should propose offsetting spending cuts to help pay for those programs and continuing expenses in Iraq.
"We're going to be in Iraq for a long time. Here's a little straight talk. And it's going to be expensive and we've got to factor that into any budgetary plans," McCain told ABC.