Former Maryland governor Martin O'Malley, a onetime Hillary Clinton loyalist, launched his White House campaign Saturday, warning the Democratic frontrunner that the presidency was not her "crown" for the taking.

Calling for a revival of an American dream he described as "hanging by a thread," O'Malley highlighted income inequality and pledged to close "a growing gap of injustice" in America should he prevail in his uphill challenge.

He hit out at "powerful, wealthy special interests" that he said have conspired to line pockets of the rich while leaving increasing numbers of Americans behind, despite more than six years with Democrat Barack Obama in the White House.

"Our economic and political system is upside down and backwards and it is time to turn it around," O'Malley told hundreds of supporters in a park overlooking downtown Baltimore.

The 52-year-old is youthful, charismatic, and brings to his campaign executive leadership experience as a two-term Baltimore mayor and two-term state governor.

But he is an unknown to most Americans who live outside the Washington-New York corridor where his political successes have been more broadly recognized.

O'Malley supported Clinton's ill-fated 2008 presidential run, but he signaled Saturday that despite her overwhelming frontrunner status, it would not be a waltz to the nomination for Clinton in 2016.

He took a swipe at the two families that have led the country for much of the past quarter century, saying he knew Wall Street would have no problem accepting another Clinton or Bush in the White House.

"The presidency is not a crown to be passed back and forth... between two royal families," O'Malley boomed, to loud applause.

In the battle for the Democratic presidential nomination, however, the 67-year-old Clinton enjoys a huge lead over her two declared rivals -- liberal independent Senator Bernie Sanders, 73, and now O'Malley.

According to RealClearPolitics.com, O'Malley polls at less than one percent to Clinton's 63.6 percent. Sanders' support is 8.8 percent.

Clinton, who reportedly received a call from O'Malley before his campaign launch, used Twitter to welcome her new rival.

"Welcome to the race, Gov. O'Malley," she tweeted. "Looking forward to discussing strong families and communities."

The narrow Democratic race could not be more different than the stampede of politicians seeking the Republican Party nomination.

Eight candidates are already in the Republican contest and eight more are all but certain to jump in, including Jeb Bush, the son and brother of two former presidents.


'Disappointed' with Hillary



O'Malley, who headed straight to Iowa to campaign in the state that votes first in the nominations process, seeks to tap into a new generation of voters disconnected from the Clintons or Bushes.

They include Baltimore resident and physician Alissa Zingman, 32, who praised the former governor for taking positions on several issues, including opposition to a huge trade accord that Washington is secretly negotiating with 11 other Pacific Rim nations.

"I've been really disappointed with how little I've seen from Hillary," Zingman told AFP at O'Malley's launch, adding that the former top diplomat "doesn't have an excuse" for not weighing in on the trade deal.

O'Malley kicked off his campaign in Baltimore, a city rocked by riots last month.

The violence highlighted aggressive "zero-tolerance" police tactics that O'Malley instituted while he was mayor. The approach lowered the crime rate but led to soaring arrests and accusations of discrimination against Baltimore's inner-city minorities.

"It was a heartbreaking night for all of us," O'Malley said.

"But there is something to be learned from that night, and there is something to be offered to our country from those flames," he said.

Opponents to the policing tactics protested near the O'Malley rally, chanting "Black lives matter" and "You are lying!"

Megan Kenny, holding up a sign that read "Stop killer cops," said she opposes O'Malley's candidacy because of the zero-tolerance polices "he designed and implemented."

"Structural racism is alive and it's working, and it needs to be dismantled, and a whole new paradigm needs to be rebuilt," she said.

O'Malley highlighted his successes in areas like education, immigration reform and same-sex marriage.

"We raised the minimum wage," he said. "We achieved top rankings for innovation, entrepreneurship, and minority and women's business development."

He also promised greater attention to climate change, improved conditions for the renewable energy industry and to rebuild American cities as places of "hope, opportunity and justice for all."