Democratic presidential candidate John Kerry is preparing to make an aggressive push for votes in several key battleground states this week as he seeks to regain political momentum in the U.S. election campaign.

Senator Kerry took a break from the campaign trail Sunday as he gears up for a major campaign swing beginning Monday on Labor Day, the traditional start of the U.S. general election campaign.

Fellow Democrats are urging Senator Kerry to be more aggressive in responding to Republican attacks and in his criticism of President Bush.

Several prominent Democrats have expressed concern about the direction of the Kerry campaign in the wake of two new public-opinion polls that give the president a double-digit lead over his Democratic challenger.

Kerry aides took to the airwaves on Sunday television talk shows in a bid to calm nervous Democrats. Kerry adviser Tad Devine spoke on Fox News Sunday.

"Incumbent presidents typically get a bounce, eight points or more," said Mr. Devine. "Incumbent presidents typically reach their high point in terms of horse race in the general election in the aftermath of their convention. So, I expect this race will soon return to where it has been for a long time. A tight horse race, which will be decided by swing voters who right now are heavily disposed against the president."

The Bush campaign is clearly pleased with the polls giving the president a boost following his convention last week. But Bush campaign strategist Mathew Dowd also predicted the race is likely to tighten over the next few weeks. He also spoke on Fox News Sunday.

"Now, will this race begin to turn back to getting much closer? Yes, it will," he said. "By the time we get to the debates, this race will be much closer. But I do think there has been a fundamental shift. It is going to be hard if they are going to defy history in order to win. Is it possible? Yes, but it is much more difficult now."

After focusing on national security and foreign policy for much of the past few weeks, Senator Kerry is now emphasizing the economy and job growth as he tours so-called battleground states like Ohio.

"This President of the United States became the first president since the Great Depression to be absolutely certain on Election Day to have not created one single new job," said Mr. Kerry.

Senator Kerry will embark on a whirlwind campaign tour Monday that will take him to a number of closely contested states, including Pennsylvania, West Virginia, Minnesota, Iowa, Louisiana and Ohio, which is perhaps the number one target state for both campaigns this year.