Presumptive presidential nominees Sens. John McCain (R-Ariz.) and Barack Obama (D-Ill.) are turning to some of their biggest-name surrogates — including top Congressional leaders — to head the “truth squads” at their opponents’ conventions this year.

McCain in particular is calling on his heavy-hitting supporters to head to Denver to try to put a dent in the Democrats’ expected boost from their four-day nominating event.

Along with key House and Senate leaders, McCain is also dispatching other GOP celebrities, like Minnesota Gov. Tim Pawlenty and Massachusetts Gov. Mitt Romney, who are thought to be on the short list for the presumptive nominee’s vice presidential pick.

“The extent of the effort is going to be staggering,” said House Chief Deputy Minority Whip Eric Cantor (R-Va.), who is headlining an event Tuesday in Denver with Romney and Reps. Marsha Blackburn (R-Tenn.) and Mario Diaz-Balart (R-Fla.).

Cantor said that during past Democratic conventions, “truth squading” has concentrated more on responding to the opposition’s message rather than driving an alternative narrative. And while GOP surrogates will certainly be in Denver to set the record straight, “in years past I don’t think we have mounted an offense during the Democrats convention and it would be a first for that. … This is an extraordinary election year, and that’s why it warrants extraordinary measures.”

Republicans in 2004 did about 200 opposition media interviews during the Democratic convention in Boston. This year, the GOP is hoping to bury that number, expecting that with so many surrogates on the ground they can reach the 1,000 mark.

Along with daily news conferences, GOP leaders will gather at a headquarters within walking distance of the convention center in Denver that will serve as a rallying point for Republicans who brave the trip next week. Matt McDonald, McCain’s top adviser for Denver efforts, said the campaign will be releasing a mix of advertisements and Web videos throughout the week and putting its top surrogates on television and broadcasting them into battleground states.

Republicans say the many new opportunities offered by the modern media environment, along with the public’s insatiable thirst for news about the 2008 election cycle, will help them drive home their slogan for the Denver convention — “a mile high and an inch deep” — during a week of expected “Obamamania.”

“There has been a very concerted effort on the part of the McCain campaign to basically counter what I perceive to be an unbelievable bias toward covering Barack Obama,” Cantor said. “I think there’s going to be a lot of glitz and a lot of hype around the convention, but our aim is talk about the reality of his voting record and his lack of leadership experience.”

Also among those being deployed is Sen. Jon Kyl (R-Ariz.), McCain’s home-state colleague and the No. 2 Republican Senate leader. Kyl will head to Denver on Wednesday night to work the media circuit and headline a press event Thursday with Pawlenty.

The duo will be tasked with trying to take on Obama’s No. 2, who will speak Wednesday night, and try to get out front of Obama’s speech Thursday night, during which he will accept the presidential nomination. Republicans are also viewing that event as a way to “turn the page” from the Democratic convention to the Republican convention in Minnesota the next week. It’s expected that McCain will make his vice presidential announcement in the days after that event.

Kyl, in a recent interview, said that while use of the opposing candidates’ surrogates during the conventions has become “standard fare,” McCain does seem to be tapping into a loyal bloc of well-placed Republicans to step in this week.

“He’s got plenty of good surrogates who have done very well on his behalf,” Kyl said. “There are two kinds of surrogates — those who have name recognition and can easily be covered, and those who have really interesting things to say.”

Kyl said his challenge over the next few days will be to “add something to the dialogue.”

“I try not to be totally partisan,” Kyl said. “But what I am hoping to do is comment in a way that has credibility, that isn’t over the top and causes people to think twice about Sen. Obama.”

Clearly, both parties are hoping to make the most of their opposition surrogates during the conventions.

Although Democrats haven’t released who will be part of their Minneapolis “truth squad,” Democratic National Committee spokesman Brad Woodhouse said the team will consist of some of the most high-profile party officials.

“You can bet we’re going to have a more aggressive counteroperation in Minnesota than what we’ve read about their effort in Denver,” Woodhouse said.

Ron Bonjean, Kyl’s former chief of staff and now a media consultant, said the practice of trying to carve out airtime during the other party’s convention has become “a new play in the communications field manual.”

No longer, Bonjean said, are candidates likely to stick to the “small fries” of previous years to articulate their message.

And these days there’s an added emphasis on having those boots on the ground in enemy territory.

In 2004, the GOP made a bit a splash by adding wayward Democratic Sen. Zell Miller (Ga.) to its “truth squad.” But Miller — who retired from the Senate after just one term — took his press calls from his home in Georgia.

Bonjean said that particularly in a closely divided race, like the one featuring McCain and Obama, candidates are going to look to their most prominent and respected backers to take up the cause.

“It shows you are taking the race seriously, but you also want to make sure your message gets heard,” Bonjean said. “Sending current and former elected officials into the fray is guaranteed to generate media coverage — not only to try to frame the message but also to try to blunt the Democrat bounce they usually get from the convention.”