Summer blockbuster brewing between Obama, Romney WASHINGTON (Reuters) - For the past three summers, President Barack Obama and his family have vacationed on Martha's Vineyard, an island retreat for the wealthy just south of Cape Cod, Massachusetts. They're unlikely to go back this year. With Obama in an increasingly heated presidential campaign and casting himself as a champion of the working class during economic turmoil, scenes of the president vacationing with the elite could be a problem. So look for the Obamas to go elsewhere - perhaps to a national park. Likewise, Republican Mitt Romney, who has been accused by Obama's campaign of killing jobs as a private equity executive, is likely to spend less time than usual at his vacation estate in New Hampshire. It's all part of the two campaigns' dueling strategies to shape their candidate's image during the political version of a summer blockbuster: roughly 12 weeks of intense campaigning and fundraising in advance of their parties' conventions. "There's going to be this competition for winning the news cycle by both campaigns that will be intense and furious," said Republican strategist Matt Mackowiak. It's a race to define the other. The summer is loaded with benchmarks that could alter the course of the race for the White House - and present a series of challenges to Obama and Romney. Within three weeks, the U.S. Supreme Court is expected to rule on whether Obama's healthcare overhaul is constitutional, a case that tests the president's signature achievement in domestic policy. Obama's campaign could get a huge boost if the high court rules in favor of the law, which requires almost all Americans to buy health insurance. But if the justices strike down that requirement or other major parts of the law, complaints by Romney and other Republicans that the law is an example of Obama exceeding his authority would have new momentum. A rejection of the law's more popular provisions - such as one that allows young adult children to remain on their parents' medical insurance until age 26 - likely would set off a scramble by both parties to find alternatives for those parts of the law. But Romney aides see victory for their side no matter how the court rules. They said Romney either would campaign against a decision upholding what he sees as a law that many Americans don't like overall, or cast Obama as a failed leader if the law is struck down. "Whichever way it comes out, it is good for us to be talking about it," one Romney adviser said. Obama's administration, meanwhile, acknowledged for the first time on Thursday that it has prepared contingency plans in case the law is rejected. "We'll be ready," Health Secretary Kathleen Sebelius said, without elaborating. Both campaigns have two dates circled on their summer calendars: July 6 and August 3, when the U.S. Labor Department will release monthly unemployment and job-creation data. The figures reported last week for May - an unemployment rate that ticked upward to 8.2 percent and just 69,000 jobs created - put Obama's team on the defensive and kicked off a week of mostly positive news for Romney. The candidates also will have opportunities to show leadership on a world stage this summer. Beginning June 18, Obama will attend the two-day Group of 20 summit in Los Cabos, Mexico, a meeting that will focus on the global economy at a time when Europe's building financial woes are threatening the United States - and Obama's re-election. During the summit, Obama is scheduled to meet with Russian President Vladimir Putin. Among the subjects likely to be on the table will be the violent crisis in Syria, where massacres of civilians have led to international calls for action against President Bashar al-Assad. Obama has been reluctant to involve the United States in the conflict and is likely to press Putin to drop his opposition to tougher sanctions against Assad. At the very least, Obama and Putin are expected to sign an agreement of cooperation, providing Obama with the type of photo opportunity that only presidents can muster. Romney, meanwhile, has said he plans to attend the "first day or two" of the Summer Olympics in London, where the Opening Ceremonies are scheduled for July 27. The visit would be a subtle reminder of Romney's experience in leading the 2002 Winter Games in Salt Lake City, and could provide voter-pleasing photo opportunities of Romney cheering for U.S. athletes. The trip abroad also could give the former Massachusetts governor a chance to visit with leaders in Europe or the Middle East. Summer is a pivotal time for presidential campaigns because it often is when the independent voters who are likely to decide the race begin to focus on the candidates and the issues, said Jen Psaki, managing director at the Global Strategy Group and a former Obama spokeswoman. "What both candidates have to do is advocate for why they're a better choice," Psaki said. For the president that means laying out the tough decisions he has made, why they were right for the economy over the medium and long term and why people should keep him in office. It also is a critical time to raise the money each campaign will need to keep going strong through the November 6 election. Obama and Romney have spent much of the past several weeks attending fundraisers that have netted each candidate several million dollars - and shed light on their target audiences. Obama's two-day trip to the West Coast this week, for example, raised about $5 million for his campaign and featured appearance with celebrities and gay-rights groups, some of whom have stepped up their donations since Obama declared last month that he supports legalizing same-sex marriages. Previously, Obama courted Wall Street donors in New York, even as his campaign was criticizing Romney's work as a private equity executive. Romney also has raised millions at New York fundraisers that targeted Wall Street, and earlier this week took in a reported $15 million during a two-day swing through Texas, a solidly Republican state that is home to some of the wealthiest donors to conservative causes. So, monthly fundraising reports will be another sign of the campaign's pulse. On Thursday, Romney's team reported raising more than $76 million in May, compared with Obama's $60 million. It was the first time Romney's monthly total had surpassed the president's. The summer campaign season will also include a barrage of advertisements on TV and the Internet that already are showing how aggressive the campaigns will be in attacking the other. Obama's campaign just unveiled one entitled "Romney Economics" that questions how successful Romney really was during his tenure as Massachusetts governor, saying he sent jobs offshore, left the state $2.8 billion in debt and that the state ranked only 47th in job creation during his tenure. Romney's ads have included one called "Symbol of Failure." The ad cites the failure of the solar energy firm Solyndra, which had received a government loan of more than $500 million from Obama's administration, as an example of how the president's economic stimulus efforts did not work and how Obama "fails to understand the nature of free enterprise in America." As his presidency has evolved into what amounts to a full-time push for re-election, Obama has appeared to relish getting back into campaign mode. At the recent NATO summit in his hometown of Chicago, he defended his campaign's strategy of attacking Romney over his career at Bain Capital, a private equity firm that sometimes laid off workers at companies it took over. "If your main argument for how to grow in the economy is, "I knew how to make a lot of money for investors,' then you are missing what this job is about," Obama said. So far, Romney's primary strategy has been to attack Obama's handling of the economy while recognizing that many Americans like the president personally. That has led Romney's team to craft a nuanced argument against the incumbent, essentially casting Obama as a nice guy who is not up to the job of being president. Romney summed up his campaign's strategy last Friday during an interview with CNBC, in which he said of Obama: "He's in over his head." Editing By David Lindsey