Obama and McCain suffer the summer-time blues as America turns off presidential politics

Despite a political environment favorable to him, Obama has yet to build a substantial lead over McCain in national opinion polls and lately has been defending himself against charges of making policy shifts to endear himself to centrist voters.

For McCain, his campaign has been unable to take advantage of the opening Obama has given him, causing concern and frustration among some Republicans who already are worried about the party's prospects in the Nov. 4 election.

National opinion polls give Obama a lead with four months to go until Election Day but his advantage is not insurmountable.

Ahead in the polls: Barack Obama addresses a town hall-style meeting in Fairfax, Virginia

Republican presidential candidate Sen. John McCain holds a news conference in Belleville, Michigan

A Pew Research Center survey conducted in late June put Obama up over McCain 48 percent to 40 per cent, while Gallup's daily tracking poll has Obama ahead 46-43.

This is despite political headwinds that face Republicans: A sagging U.S. economy, $4-a-gallon gasoline and an unpopular Republican President George W. Bush.

Political experts say voters still appear to have some doubts about the 46-year-old Obama, a first-term Illinois senator.

"He still has not crossed the threshold of the voters' comfort level," said Democratic strategist Bud Jackson. On the other hand, said Jackson, "he already has a lead despite the fact that he is less well-known and he has more room to gain than John McCain."

Another Democratic strategist, Jim Duffy, said the usually sure-footed Obama camp's handling of a controversy over his policy shifts has raised eyebrows.

Among recent shifts in tone was Obama's comment last week that he reserved the right to "refine" his Iraq policy, after pledging for months that all U.S. combat troops would be out of Iraq in 16 months.

Ready for action: Republican presidential candidate John McCain and his wife Cindy are in for a long summer of campaigning

Last few months: President George Bush

"I'm not willing to say it's big trouble," Duffy said. "But the way they're handling it, if you're an Obama supporter, isn't necessarily giving you a whole lot of confidence right now. They don't seem to be able to slip this punch right now."

McCain, 71, an Arizona senator, has suffered several missteps that have cost him valuable time arguing his case.

Another day on the trail was lost on Thursday when a McCain economic adviser, former Texas Republican Senator Phil Gramm, told The Washington Times that Americans are in a "mental recession" and have become a "nation of whiners."

"Phil Gramm does not speak for me," McCain told reporters, after months ago holding Gramm up as one of the advisers he relies on for economic wisdom.

And on Wednesday, McCain found himself having to explain a remark he himself made, that it was an "absolute disgrace" that young people were paying taxes to support the Social Security system for retirees.

Senate Majority Leader Harry Reid, a Nevada Democrat, was quite happy to point out to McCain that "this is how Social Security was designed to work."

Republicans are hoping a McCain campaign makeover engineered by former proteges of Bush's ex-political guru Karl Rove will quickly bring some change.

They complain that McCain, a Vietnam war hero with a solid reputation, has yet to offer a central theme as to why voters should choose him over Obama.

"Everybody is certainly waiting to see what his central message and theme is going to be," said Republican pollster Tony Fabrizio. "I'd say we're waiting with bated breath."

Democrats still like their chances with Obama, pointing to the leads the Democrat has in several battleground states that will help determine the outcome of the race.

"If he keeps doing what he's doing and McCain is unable to undermine him, he wins the election," said Democratic strategist Doug Schoen.

What would help both sides for the battles ahead, said Republican strategist Rich Galen, is a little summer down time.

"Everybody's been at it for so long," he said. "What they ought to do is call a time-out for the rest of July, everybody go on vacation."