"We begin a great journey, a journey to take our country back and fundamentally change the nature of our politics," Obama said in an online video sent to supporters, reported Agence France-Presse (AFP).
Launching a historic quest to be America's first black president from the Midwestern hometown of Abraham Lincoln, the US icon who freed the slaves, Obama will ride a tide of hype into a packed Democratic field dominated by Senator Hillary Clinton and 2004 Democratic vice presidential pick John Edwards.
The 45-year-old, whose dazzling rhetoric has evoked whispered early comparisons to past political giants like John F. Kennedy, must confront critics who say he is an upstart, low on experience and about to find lofty idealism can be left in tatters by bare fisted campaign combat.
He must also confront the mighty Clinton election machine. The former first lady's ruthless political streak, money raising muscle, powerful friends and of course her charismatic husband former US president Bill Clinton, have already put her at the front of the field, according to most polls.
"I know a lot of you are cynical about the possibilities of that change — sometimes it seems as if the game is fixed, and it only works for the few and the powerful," Obama said in his message.
"But, I fundamentally believe there is another brand of politics," Obama said, as he leapt into a presidential race moving at unprecedented speed nearly two years before Americans chose their 44th president.
A resume packed with achievement includes Obama's role as the first black president of the elite Harvard Law Review. His childhood, however, was tough owing to his parents broken marriage.
When his mother remarried, he lived for several years with his new stepfather in Indonesia, an experience, he told AFP in an interview, which opened his eyes to wrenching poverty around the globe.
After his announcement on Saturday, Obama will bound onto the campaign trail in Iowa and New Hampshire, nearly a year before the two states hold early nominating contests for the Democratic and Republican presidential tickets.
Obama, son of a Kenyan economist and a white mother from the US heartland state of Kansas, laid out a idealistic blueprint for his campaign, betting that the Americans are yearning for change.
But Obama's status as the first black presidential contender considered to have a real shot at winning the White House has not translated into automatic black support.
Analysts were not surprised as Obama is a relative newcomer on the national stage and, unlike many established black leaders, did not build his reputation during the civil-rights struggles of the 1960s.
"People don't know who he is. Outside of Illinois, black voters and everybody else are asking, 'Who is this guy?'" Ron Walters, a former adviser to civil rights leader Jesse Jackson and head of the African-American Leadership Institute at the University of Maryland, told Reuters.
"They don't know his record, they don't know his background or where he came from, so they are asking very understandable questions," he said. "He has to win their vote like anyone else."
Jackson, a veteran of losing Democratic presidential campaigns in 1984 and 1988, has not endorsed Obama. Neither has the Rev. Al Sharpton, a Democratic presidential candidate in 2004 who has not ruled out another run.
Polls show Clinton is favored by a majority of black voters, with Obama a distant second. Clinton, whose husband President Bill Clinton is popular with black voters, receives much higher favorable ratings from blacks than Obama.
Edwards, a former senator from North Carolina, also is making a concerted pitch for black support and launched his campaign in December from a poor, primarily black New Orleans neighborhood ravaged by Hurricane Katrina.
But polls show blacks oppose the Iraq war at higher percentages than white voters, making Obama's early opposition to the war a potential selling point.
Black voters constitute about 10 percent of the US electorate, and they often make up more than 40 percent of the Democratic primary vote in key Southern states like South Carolina, the fourth state to cast ballots in the 2008 Democratic nomination race.Güncelleme Tarihi: 20 Eylül 2018, 18:16