The U.S. presidential campaign has grown increasingly personal and negative in recent days, as public opinion polls show Democratic candidate Barack Obama moving into a lead over Republican John McCain.  VOA National Correspondent Jim Malone has been monitoring the back and forth on the campaign trail and has more from Washington.

Both candidates have been campaigning in key battleground states - closely contested states that could tip the election one way or the other on November 4.

Grim economic news appears to be hurting Republican John McCain.  Most polls give Democrat Barack Obama a consistent lead with less than four weeks to go until Election Day.

Senator John McCain in Waukesha, Wisconsin, 09 Oct 2008

Increasingly, Senator McCain is trying to make Senator Obama the main issue in the campaign, as he did during a recent rally in Pennsylvania.

"In short, who is ready to lead in a time of trouble and danger for our country?  Who will put our country first?  And which candidate's experience in government and in life makes him a more reliable leader for our country," asked John McCain.

The McCain campaign has raised questions about Obama's background and past associations.

A favorite target is William Ayers, a former member of the anti-Vietnam War Weather Underground group.  Ayers lives near Obama in Chicago and hosted a political reception for Obama 13 years ago.

The Obama campaign says the two men are not close.  But Senator McCain told Fox News that voters should know more about their relationship.

"It's about Senator Obama being candid and straightforward with the American people about their relationship," he said. "He has dismissed it by saying he was just a guy in the neighborhood.  We know it was much more than that.  Let's reveal all the details of that relationship and then the American people can make a judgment."

McCain is also under increasing pressure from supporters to go after Obama personally and remind voters of Obama's ties with his controversial former pastor, the Reverend Jeremiah Wright.

One voter challenged both McCain and his vice presidential running mate, Alaska Governor Sarah Palin, during a recent rally in Wisconsin.

"When you have an Obama, [Democratic House or Representatives Speaker Nancy] Pelosi and the rest of the hooligans up there who are going to run this country, we have got to have our head examined!  It is time that you two [McCain and running mate Sarah Palin] are representing us, and we are mad!  So go get them," said the voter.

Democrats have urged Obama to fight back against the attacks, mindful of the negative attacks ads that helped undermine the 2004 Democratic nominee for president, Senator John Kerry.

Senator Barack Obama campaigning in Cincinnati, Ohio, 09 Oct 2008

But during a recent rally in Ohio, Obama kept his focus squarely on the economy.

"I can take four more weeks of John McCain's attacks, but America can't take four more years of John McCain's-George Bush's policies," he said. "We can't afford four more years of the same!"

But Obama has launched his share of negative attacks.

He reminded supporters in Ohio about McCain's decision to suspend his presidential campaign to work on a congressional economic bailout package shortly before the first presidential debate.

"I don't think we can afford that kind of erratic and uncertain leadership in these uncertain times," he said. "We need steady leadership in the White House.  We need a president we can trust in times of crisis.  And that is why I am running for president of the United States!"

Both campaigns have also taken to the television and radio airwaves and the Internet with attack ads.

McCain campaign ads question Obama's policies and seek to counter Democratic attacks on McCain.

"Obama's stem cell attack:  not true.  Barack Obama:  he promised better.  He lied.  I'm John McCain and I approved this message," says one ad.

A study by the University of Wisconsin in Madison found that most McCain ads last week attacked Obama, while only 34 percent of Obama spots directly targeted McCain.

Nevertheless, experts say both sides are firing negative ad salvos with abandon, including the Obama campaign.

"With no plan to lift our economy up, John McCain wants to tear Barack Obama down with smears that have been proven false.  I'm Barack Obama and I approved this message," says one ad.

Experts say the shift to a negative tone late in the presidential campaign is predictable, but it may not produce the desired results.

"McCain is trying to change the subject and he is using all the materials at his disposal," said Larry Sabato, who directs the Center for Politics at the University of Virginia. "But probably this isn't going to work."

Sabato adds that negative campaigning is not likely to alter an environment where voters are most concerned with the troubled domestic economy and want the candidates to present solutions.

"There are small bore [minor] elections and there are big issue, big change elections,' he said. "This is a big issue, big change election.  And in that sort of election, it doesn't matter terribly that these kinds of attacks are being made because that is not how the vast majority of votes will be determined."

Experts say McCain's best chance to alter the focus of the campaign could come in the third and final presidential debate next Wednesday at Hofstra University in New York.