The retired four-star general, a decorated Vietnam veteran who headed the 1999 bombing campaign in Kosovo but opposed the Iraq war, said he would restore a sense of confidence and optimism to Americans facing job losses and worries about their safety.
“We can do better, we will do better, and we will do it together," Clark told a rally in his hometown of Little Rock in the state of Arkansas on Wednesday that kicked off his late-starting campaign.
The announcement by Clark, who has no national political experience, makes him the 10th candidate in the crowded field of Democrats vying to challenge Bush.
War campaign issue
It comes four months before the first major nominating contests in Iowa and New Hampshire and shakes up a volatile race that has focused on the Iraq war and the stumbling economy.
Clark, who announced he was a Democrat earlier this month, promised to ask tough questions of Bush.
“At times of great historic challenges, the American people deserve to hear the truth and hear it in plain and simple language," said the former Rhodes scholar, who finished first in his class at West Point.
He criticised Bush for presiding over the loss of nearly 3 million jobs, rising budget deficits and threats to civil liberties and personal safety.
“For the first time since the 1960s and 1970s, more than 100,000 troops are fighting abroad and once again Americans are concerned about their civil liberties," Clark said. "For the first time since the Cold War, many Americans no longer feel safe in their homes.”
Clark joins nine other Democrats
in the crowded 2004 race
Clark's supporters hope his military credentials put him in a prime position to challenge Bush's role as commander-in-chief.
But Clark also could damage several Democrats in the race, most notably Massachusetts Senator John Kerry, the only military veteran in the race until Clark's arrival, and former Vermont Governor Howard Dean, who rode to the front of the pack as an outsider who opposed the Iraq war.
Few rank-and-file Democrats know much about Clark beyond his military record and his views on the Iraq war. While he enters the race late, polls have shown many Democrats are undecided or have not started paying attention to the 2004 race, giving him time to catch up.
"The 21st century is going to be an American century, just like the 20th century was,” he vowed.
Clark will not be starting his campaign entirely from scratch. He has attracted strong grass-roots support on the internet and a Draft Clark website has gathered pledges of more than $1.6 million that will be turned over to him.
Although a team has not been announced for the Clark run, Mark Fabiani, an adviser to fellow Arkansan and former President Bill Clinton, has taken a prominent position in organising his campaign.