By Major Garrett

RALEIGH, N.C. -- Barack Obama's campaign plans to use the four-day Democratic National Convention next week to relentlessly portray John McCain as a carbon copy of President Bush, in a strategic shift foreshadowed by two days of tougher attacks on his GOP rival.

The criticism itself, which will focus on the Arizona senator's economic policies, ties to lobbyists and decades-long tenure in Washington, is not new. But the intensity of the attacks is -- and it is meant to minimize the heavy emphasis on Obama's charisma-driven campaign.

McCain has hammered the theme in recent weeks that Obama is an aloof "celebrity" unprepared to be commander in chief.

"The convention will offer a series of contrasts and comparisions of the McCain record so voters can see how clearly the choice will be in November," Obama spokesman Bill Burton told FOX News. "The convention will also introduce Senator Obama to the country, but it will make sure to convey strongly the differences and choices Obama's campaign presents over McCain's."

The move is a rejection of John Kerry's decree in 2004 that his convention would project a positive message about Kerry and the Democratic Party while minimizing attacks on President Bush and the GOP.

Obama strategists believe Kerry's convention was too passive and gave Bush and the Republicans space to create their own message without having to respond to Democratic criticisms. Advisers say the convention contrasts will not be personal, but will cast a harsh light on McCain's record, lobbyist relationships and similarities with Bush. Aides say the campaign is setting out to offer a stark contrast between McCain and Obama.

The convention will naturally highlight Obama's biography and serve as the broadest platform to date to introduce Obama to the country. But far more memorable may be the speeches that attack McCain on the economy and portray, for example, his newfound commitment to offshore oil drilling as an industry-driven flip-flop rather than a shift driven by new facts and circumstances -- as McCain characterizes it.

The past few days on the campaign trail serve as a prelude to the tone the Democratic convention is expected to take next week.

Here's how Obama's camp described McCain's visit Tuesday to an offshore oil rig near New Orleans.

"For three decades, as our energy crisis grew, decision-making in Washington has been rigged against our national interests and the interests of American consumers," Obama spokesman Tommy Vietor said in a statement. "And for almost that long, Senator McCain has been part of the problem. For decades, he has stood with the big oil companies and voted against the development of the alternative energy we need."

Obama's camp offered another taste of things to come with biting remarks about McCain's approach to politics and policy. Tuesday at the national Veterans of Foreign Wars convention in Orlando, Fla., Obama struck back at McCain's speech to the same group the day before.

"Instead of just offering policy answers, he turned to a typical laundry list of political attacks," Obama said. "He said that I have changed my position on Iraq when I have not. He said that I am for a path of 'retreat and failure.' ... That is John McCain's prerogative. He can run that kind of campaign, and -- frankly -- that's how political campaigns have been run in recent years. But I believe the American people are better than that."

Obama said Monday in New Mexico that McCain's support for Bush-era tax cuts renders him out of touch with the concerns of average Americans. Obama also said McCain's political advisers don't know how to debate issues, so they've resorted to undermining Obama personally.

Obama's strategy does not come without risks.

It could damage Obama's image as a rise-above-it politician who doesn't want the campaign to become an endless series of charges and counter-charges. Engaging McCain and attacking him could allow McCain to say Obama's not really a new and inspirational leader, but a brass-knuckle politician like all the rest.

Also, it was Kerry's emphasis on a positive message that allowed Obama to wow the convention floor and first attract national attention with his upbeat keynote address in 2004.

Even so, Democratic strategists say Obama needs to toughen his stand on McCain, and the convention is the best place to start.

"They do not feel like they're slipping (in the polls), but they just think they need a clear definition of McCain supporting Bush economic policies, as well as being totally a D.C. figure," said one Democrat familiar with the Obama campaign's thinking.

As for the risks of "going negative," another top Democratic strategist said it's not a close call.

"He needs to do it because if you don't fight back voters think you won't fight for them," said Mary Anne Marsh. "Therefore you have to do it to win their support. The benefit outweighs the cost."

But other Democratic strategists wonder if taking on McCain might backfire, provoking sympathy for a Vietnam War hero who prior to the campaign had built a reputation as a GOP maverick who defied lobbyists by pushing campaign finance reform and sought to block pork-barrel spending.

"The question would be, 'How would McCain respond?'" said one Democratic strategist. "Typically, you would want the status quo of this campaign to continue (in a pro-Democrat year in the polls). It's risky. They must have polled this and focus-grouped it."