* Opening his presidential campaign, the Massachusetts senator plays up his military credentials and takes swipes at Democratic rival Howard Dean and President Bush.

MOUNT PLEASANT, S.C. - With a warship for a backdrop and his Vietnam combat comrades by his side, Sen. John F. Kerry of Massachusetts stood yesterday on a key political battleground of the South to formally kick off his presidential campaign.

Or is it the Stop Dean campaign?

The well-financed Kerry, once widely seen as the lone Democrat with the credentials to challenge President Bush's credibility on issues of war and peace, now finds himself under pressure to slow the advance of an upstart antiwar candidate, Howard Dean, who suddenly leads the field in key states and threatens to ride a wave of partisan anger to the presidential nomination.

After months on the campaign trail, Kerry is reintroducing himself to voters with his "American Courage Tour," a series of speeches lashing out at what he calls "George Bush's radical vision" and taking some swipes at former Vermont Governor Dean.

In an interview, Kerry portrayed the tour - appearances in South Carolina and Iowa yesterday, in New Hampshire today and in Boston tonight - as an opportunity to present himself as a national candidate with a clear rationale for replacing Mr. Bush. The tour also represents the launch of the fall campaign, when Americans may begin to tune in more closely to such events as a series of Democratic debates beginning tomorrow in New Mexico.

Kerry raised the bread-and-butter issues that usually decide presidential campaigns, accusing Mr. Bush of an economic policy that "comforts the comfortable at the expense of ordinary Americans" and has led to the loss of more than 3 million jobs since he took office.

In the war on terrorism, Kerry charged that Mr. Bush "has squandered the goodwill of the world after September 11 and lost the respect and influence we need to make our country safe." Regarding Iraq, he said Mr. Bush "was wrong to rush to war without building a true international coalition - and with no plan to win the peace."

"Being flown to an aircraft carrier and saying 'Mission accomplished' doesn't end a war," he said. The decorated veteran thus chided Mr. Bush - whose Vietnam-era service in the Texas Air National Guard did not include combat - for his May 1 speech aboard the Abraham Lincoln, during which he declared an end to "major hostilities" in Iraq.

But by his very choice of the star-spangled setting - beside the aircraft carrier Yorktown, in a conservative Southern state - Kerry drew attention to a dilemma that is central to his own campaign and to his party's choice of a presidential nominee.

"KERRY'S PROBLEM is that on the single most visible issue that moves Democratic activists - the war in Iraq - Dean seems more in step with the instincts of Democratic activists," said Stuart Rothenberg, an independent political analyst in Washington.

"Kerry was with the president" in voting for the congressional resolution authorizing Mr. Bush to go to war, Rothenberg noted. "And since then he's been on any and all sides of the issue, sometimes with good reason," because the issue has its complexities.

"Dean has a much cleaner message - he might be wrong ultimately - but his message is very simple: the president is wrong, the war is wrong," Rothenberg said.

Even for cheering campaign audiences - about 700 here yesterday morning and more than 1,000 last night in Des Moines, Iowa - Kerry took pains to describe the nuances of how he stopped short of giving Mr. Bush a green light to make war. "I voted to threaten the use of force to make Saddam Hussein comply with the resolutions of the United Nations," he said - an inadvertent reminder of a cerebral approach that some observers see in Kerry.

"You can't be senatorial in a presidential race," said Alan J. Lichtman, a history professor at American University. "That's one of the reasons why we haven't elected a senator president since John Kennedy. The legislative model is not the presidential model - compromising, conciliating, looking at the pros and cons of the issue - that doesn't work. If you look at the great presidents, they seized opportunity, took risks."

Dean took the gamble of attacking Mr. Bush on Iraq - loudly, harshly and early - and of chastising Democrats who supported the war, including Kerry, Sen. Joseph I. Lieberman, D-Conn., and Rep. Richard Gephardt, D-Mo.

Because their criticism of Mr. Bush's postwar policy "sounded equivocal," said Lichtman, "Dean rushed in to seize a space of deep opposition to President Bush, sounding in a clear liberal voice a clarion call to reclaim traditional Democratic values."

Liberal partisans always dominate the Democratic party's early fundraising and the organizing in the first two key contests, the Iowa precinct caucuses and the New Hampshire's first-in-the-nation primary, both held in January.

FOR THE 2004 election, "the party activists are energized to go with their heart more than their head because of their intense hatred for George Bush, because of the general unhappiness with events both on the economy and on Iraq, and because of Democratic anger left over from the contested 2000 election," said Larry Sabato, a political scientist at the University of Virginia.

Thus, he said, the Democratic race shapes up at this moment as a contest between Dean and whoever emerges as the alternative to Dean - perhaps Kerry if Dean beats Gephardt in Iowa, where Gephardt is well known and liked; perhaps Gephardt if Dean beats Kerry in New Hampshire; perhaps Lieberman or North Carolina Sen. John Edwards if Dean wins both early contests.

Kerry and his advisers reject such analysis. Kerry said, for example, that he is "absolutely not" looking to the early February South Carolina primary - where his military credentials would appear to be popular - as a base for a comeback if he has disappointing showings in Iowa or New Hampshire.

Kerry said Dean has done "a spectacular job" in fundraising, connecting with voters and other aspects of the campaign. But he and his advisers also said that Dean's early lead in New Hampshire, for example, is partly the result of heavy summer advertising.

Campaign aides said Kerry will soon begin to advertise in some of the early-contest primaries, including Iowa and New Hampshire.

Kerry fundraiser Bob Farmer said he expects Howard Dean to raise $12 million or more during the quarter that ends Sept. 30. "That will put him just about even with us in cash on hand," he said, noting that Kerry finished a close second to the leading Democratic fundraiser in each of the first two quarters of the year.

KERRY PACKED his six-page speech with references to his positions on key issues.

* On taxes, he said he would "roll back the Bush tax cuts for the wealthy so we can invest" in pressing domestic programs. "Some in my party want to get rid of all [Mr. Bush's] tax cuts - including those for working families," such as the hike in the child tax credit and the repeal of the so-called marriage penalty. That was a criticism of Dean and Gephardt, who have called for the repeal of all the cuts to pay for other programs.

Kerry also pledged to reform and simplify the tax system.

* On gun control, Kerry said, "Courage means standing up for gun safety, not retreating from the issue out of political fear or trying to have it both ways. I'm a hunter and I believe in the Second Amendment, but I've never gone hunting with an AK-47." That, he later acknowledged, was a dig at Dean - a rare Democratic presidential hopeful who opposes many forms of gun control.

* On energy, he pledged to push Detroit to improve gasoline mileage, part of what he has called a "Manhattan Project" to develop new energy sources that will wean the United States off its dependence on oil imports.

* On the environment, he said Mr. Bush's "Clean Skies initiative actually means dirtier air; his Healthy Forests proposal actually means cutting down trees. He proposed to let his oil industry friends drill in the Alaska National Wildlife Refuge." Kerry helped to kill that plan in the Senate.

Lichtman said a primary schedule that may determine the nominee in early March has made the fall more important than ever and is putting enormous pressure on Kerry and the other Democrats to match the pace Dean has set.

"I'm a Red Sox fan," said Kerry communications director Chris Lehane. "There's a big difference between being hot in the summer and being hot in the fall."