New public opinion polls are painting a contradictory picture of the U.S. presidential race, even as Democrat John Kerry tries to sharpen his policy differences with President Bush.

There was good news for the Bush campaign in the latest Gallup poll, which gave the president a lead of 54 to 40 percent over Senator Kerry. However, two other recent polls, one by the Harris polling firm and another by the Pew Research Center, found the race had slipped back to a dead heat between the two candidates.

Most recent polls have indicated that President Bush had surged into a solid lead following the Republican convention earlier this month. But Democrats have seized on some of the newer polls that suggest the president's lead has narrowed, and that the race is once again tightening.

The somewhat contradictory polling data comes as Senator Kerry steps up his criticism of the president on his handling of both Iraq and the domestic economy.

"Our president has made serious mistakes in taking us to war in Iraq." said John Kerry. "[He was] wrong to rush to war, without the major allies that could have been with us helping us. So, when it comes to Iraq, it is not that I would have done just one thing differently, I would have done almost everything differently."

The new Kerry approach also comes in the wake of changes within the Kerry campaign that include the addition of several political advisors who used to work in the Clinton administration.

Kerry supporters, like Evelyn Hein from Allentown, Pennsylvania, say they welcome the Democratic candidate's more aggressive approach against the president.

"And I think John Kerry should to get a little tougher with the opposition," she said. "I want to hear him say what he is going to do, not so much dwelling on the past, but what we can do in the future."

President Bush remains upbeat about Iraq, the economy and the war on terrorism as he campaigns around the country.

"Because we acted, because we led, the government of a free Afghanistan is fighting terror, Pakistan is capturing terrorist leaders, Saudi Arabia is making raids and arrests, Libya is dismantling its weapons program, the army of a free Iraq is fighting for freedom and more than three quarters of al-Qaida's key leaders and associates have been brought to justice," said President Bush.

The Bush campaign can also take comfort from some new polls in individual states that suggest the president is doing well in states like Wisconsin and Minnesota. These are states Democrat Al Gore won four years ago, and a strong Bush effort in both would force the Kerry campaign to divert resources from other competitive states that the Democrats need in order to win in November.

The latest polls also suggest voters, at least for now, prefer the president's approach on both Iraq and the war on terrorism.

Newsweek magazine political analyst Howard Fineman told NBC television that Senator Kerry's shifting positions on Iraq have given the president an opening he has exploited on the campaign trail.

"In a presidential campaign, you have to be clear, you have to be consistent, you have to be repetitive," said Howard Fineman. "George Bush's campaign is well run, well focused, and so that is Number One. Number Two, war is the big issue on the minds of most voters."

For months now, the polls have indicated that voters have confidence in the president's ability to lead the war on terrorism. But the public's view of his handling of Iraq appears to be more volatile, with support moving up or down, depending on the level of violence in Iraq.

Stuart Rothenberg publishes a political newsletter here in Washington. He says the president has done an effective job, so far, of convincing voters that the struggle in Iraq is part of the overall war on terrorism.

"I think, if the voters evaluate George Bush generally on terrorism, I think that is an asset for him," he said. "If the voters look specifically about Iraq and casualties and car bombs and things like that, then it is not nearly as good for the president."

Kerry supporters are now looking ahead to the presidential debates as their best opportunity to narrow the gap with President Bush. The first debate is scheduled for September 30 in Florida.