With July 4th in the rear view mirror and the end of summer's political conventions fast approaching, John McCain and Barack Obama have a scant seven weeks to tackle major issues: retooling their campaigns for the general election, cementing their brand image and finding running mates.

In the midst of it all, they also need to reintroduce themselves to a broad swath of voters who may not have been paying attention to electoral politics since their own state's primaries.

Gearing up for an ambitious and offensive 50-state strategy, Obama is moving to shed his liberal image and put a finer point on his working-class values after losing those voters to Hillary Clinton during the primary.

McCain is making clear he's no 20th century dinosaur. His new slogan, "reform, prosperity and peace," is a far cry from the Winston Churchill-invoking Web ad from March that featured McCain declaring, "We're Americans, and we'll never surrender. They will."

"It's clear that Obama has begun the classic swim to the middle," said Jeremy Mayer, public policy professor at George Mason University. With McCain, "he still wants to present himself as the maverick Republican ... There's been a bit of schizophrenia in his presentation."

In the early weeks of the presidential race, Obama still has a front-runner glow. He is leading in almost every national poll and pulling ahead in critical battlegrounds. On controversial issues -- most recently, gun control and Iraq -- he's no longer playing for the hard left of his party.

McCain is in a whole different game -- taking on the scrappy underdog role. Like Clinton did in the closing weeks of her failing primary bid against Obama, McCain is challenging the presumptive Democratic presidential nominee to debates and forums the Illinois senator so far has no intention of joining.

"I'm the underdog. I'm behind," McCain said last week. "I've got to catch up and get ahead. And I expect to do that about 48 hours before the general election."

Obama, the "Post-Partisan Candidate," Tries to Please Left and Center

In 2007, the National Journal ranked Obama the most liberal U.S. senator. However, his public policy positions lately seem out of character with that title, as he tries to craft an image of the candidate who transcends partisanship and can usher in a shinier, better America.

But Obama must first undo the perception that he's a "radical," Mayer said.

"He's trying to pass that very unquantifiable test of looking presidential," Mayer said. Fortunately, he added, his credibility with the Democratic base will enable him to swim toward the center to counter that radical perception.

Last week, Obama denied he was moving to the center, but several of his positions have called that claim into question.

When the Supreme Court ruled two weeks ago that child rapists could not be sentenced to death, Obama sided with McCain in opposing the ruling. When the same court ruled that Americans have a constitutional right to keep guns in their homes for self-defense, in turn invalidating a 32-year-old ban on handguns in Washington, D.C., Obama and McCain both agreed with the decision.

That seemed to run counter to a statement Obama's campaign put out last year that said the handgun ban was "constitutional."

Obama also said this past week that he's willing to "refine" his Iraq policy -- though he insisted his plan to withdraw troops within 16 months of taking office remains unaltered.

Meanwhile, the Illinois senator is emphasizing his upbringing, personal values and support of faith-based initiatives.

Obama stressed the themes of national service, faith and patriotism in separate speeches this past week -- all designed to build walls against attacks on his character and construct bridges to voters waiting to learn more about him.

Shedding light on his roots in his first major TV ad of the general election, called "Country I Love," Obama highlighted how his single mother and grandparents taught him values straight from the "Kansas heartland where they grew up."

He frequently wears a flag pin -- something he was criticized by Republicans for not doing during the primary.

And on Monday, the man who wants to lift the national rhetoric obliquely criticized the liberal advocacy group MoveOn, which endorsed him months ago but also came under heavy fire last year for running an ad that referred to Gen. David Petraeus as "General Betray Us."

Obama referenced the flap when he said: "All too often, our politics still seems trapped in these old, threadbare arguments, a fact most evident during our recent debates about the war in Iraq, when ... a general providing his best counsel on how to move forward in Iraq was accused of betrayal.

McCain the Maverick Asserts Independence, Stays the Course in Iraq

McCain will have less work to do than Obama to appeal to a middle-of-the-road constituency, since he is already seen largely as a center figure in American politics, said Mayer.

But image-crafting has its risks. McCain is already on shaky ground with conservatives, though he has worked to mend fences.

Still, moderate voters swing elections. A June FOX News/Opinion Dynamics poll found that 16 percent of voters consider themselves independents. That's a far larger percentage than the gap that separates McCain and Obama in national polls.

McCain is also trying to foster a patriotic image. At a town hall meeting stacked with McCain supporters, questioners last month praised him for his military service and called him a "hero."

For McCain, the biggest challenge to closing the polling gap with Obama will be to distance himself from President Bush. On June 3, the night Obama secured the Democratic delegates to win the nomination, McCain insisted he is not, as Democrats charge, running for a third Bush term.

He has called such claims "false," and highlighted his past disagreements with Bush over detainee treatment, federal spending, climate change and energy policy.

But McCain, a Vietnam POW, is tied to Bush in that he supports a stay-the-course approach in Iraq. In his first general election ad, he says he's running "to keep the country I love safe," but adds, "Only a fool or a fraud talks tough or romantically about war ... I hate war."

Polls consistently show McCain is more trusted on issues of national security than Obama while Obama leads McCain on domestic issues like the economy and energy. GOP strategist Anne Dickerson said the Republican can use that trust to build his role as the responsible commander-in-chief in war time.

"(Obama's) acting like a community activist and not a global leader," said Dickerson, who worked on Rudy Giuliani's campaign during the GOP primary and now fundraises for McCain.

"John McCain has the right and the duty to argue that," she said.

As voters list the economy as their No. 1 priority this election, McCain is putting extra emphasis on his quest for energy efficiency. He's recently offered a $300 million prize to the inventor of a superior car battery and a $5,000 tax credit to buyers of cars with zero carbon emissions; and he's called on the federal government to switch to green technologies.

McCain also pledged last week to a group of Latino officials that he would make immigration reform a "top priority" during his first 100 days in office.That's a turnaround from his refusal to say, during a January debate, whether he'd vote for his own immigration proposal, with its guest worker provisions, if it came to the Senate floor.

Candidate Crossfire

The presidential contenders are doing everything they can to design fashionable labels for themselves, but they are also working on crafting unflattering caricatures of each other. That branding could be far more influential to voters' perceptions.

Obama's depiction of McCain has been crystal clear since he clinched the Democratic nomination. McCain is an older and more tired third Bush term -- and despite his maverick record he's traded in his independent stripes to run for president.

"Bush is a millstone around his neck, and unless he can get to the center, he can't win. It's just impossible," said Democratic pollster Doug Schoen.

In practically every move McCain makes -- from traveling to Latin America to promote free trade to reversing position to support lifting a ban on offshore oil drilling -- the Obama campaign says McCain is mimicking the current, unpopular president.

"While John McCain can legitimately tout moments of independence from his party in the past, such independence has not been the hallmark of his presidential campaign," Obama said in St. Paul, Minn., when he clinched the nomination. "It's not change when John McCain decided to stand with George Bush 95 percent of the time, as he did in the Senate last year."

McCain must also ward off claims that he's too old for the job. At 72, he'd be the oldest president sworn in for a first term. Picking a young vice presidential running mate could help alleviate concerns about his age, though it's unlikely to draw the youth vote from Obama, who is wildly popular among 18- to 29-year-olds.

Meanwhile, McCain's depiction of Obama is a work-in-progress.

He's been criticized for failing to settle on a single attack strategy for Obama and testing a series of trial balloons.

In the past few weeks, Obama has been a liberal, a big spender, a pessimist, a flip-flopper and a typical politician, according to the McCain campaign.

McCain has recently started to settle on a theme that Obama is not trustworthy, and that he will do anything to protect his political advantage. He points to Obama's recent reversal to opt out of public financing to make his case.

"You know, this election is about trust, and trusting people's word," McCain said at a Saturday fundraiser in Louisville, Ky. "And unfortunately, apparently on several items, Senator Obama's word cannot be trusted."

However, McCain seemed to undercut his own message Thursday when he told FOX News he still thinks that, overall, Obama is "trustworthy."

FOX News' Major Garrett and Carl Cameron contributed to this report.