(CNN) -- Sen. John McCain, the presumptive Republican presidential nominee, is settling on a message.

Sen. John McCain's advisers say his experience as a prisoner of war shows he's willing to put his country first.
First, he's portraying his rival, Sen. Barack Obama, as a typical politician -- despite all that talk from the Illinois Democrat about change and his ability to reach across the aisle.
As an example, the McCain camp is pointing to Obama's recent decision to drop out of the public campaign financing system after realizing his campaign had turned into a cash machine.
Obama "has consistently voted with his party on the most partisan issues and put his party and personal interests ahead of those of the nation," said former Massachusetts Gov. Mitt Romney, once a 2008 GOP presidential candidate and now a McCain backer.
The second part of the Republican's strategy, as laid out in a memo to reporters from adviser Steve Schmidt, is to recall McCain's time as a prisoner of war during the Vietnam War to show his toughness and willingness to put his country first.
"When John McCain was offered early release as a prisoner of war, he refused, subjecting himself to torture rather than give a propaganda victory to his captors," Schmidt wrote.
Watch analysts debate whether McCain's strategy will be effective »
Another example of McCain's toughness, Schmidt said, occurred when he bucked his party to work with Democrats on immigration reform.
Linking McCain's POW experience to his work with Sen. Edward Kennedy, D-Massachusetts, on an immigration bill may seem like a stretch, but the point is that McCain's camp is casting its guy as someone who takes on tough fights.
"They're defining him as a fierce patriot who strongly loves his country and will do anything to sacrifice himself, anything for the better of the country," said Republican strategist John Feehery, "and I think it's actually a nice contrast to Barack Obama, who is kind of a Johnny-come-lately."
Watch how disgruntled conservatives worry McCain's camp »
Highlighting the Arizona Republican's maverick image is also a way to contrast McCain with President Bush as Democrats attempt to tie the presumed GOP nominee to the unpopular president.
But is the McCain strategy accurate, and will it work?
Obama also has gotten credit for reaching across the aisle during his time as an Illinois legislator and in the U.S. Senate. One Republican whom Obama has worked with, Sen. Gordon Smith of Oregon is even touting the Democrat's independent credentials in a campaign ad of his own.
"Who says Gordon Smith helped lead the fight for better gas mileage and a cleaner environment? Barack Obama," the announcer says in a Smith ad.
And Obama is putting his own twist on the charge he's just a "machine" politician from Chicago, Illinois.
At a news conference Wednesday, Obama defined his approach to politics as "Midwestern in some ways, which is important and will represent a significant change from the very ideological, very sharp partisanship that we've seen in Washington."

Obama allies also point out that Sen. Hillary Clinton used some of the McCain strategy in the Democratic primaries -- particularly the part about being a tested leader -- and failed to prevent her rival from becoming the party's standard bearer.
But now it's McCain's turn to try to define himself -- as ready to lead on Day One.
All About John McCain • Barack Obama • Gordon Smith
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