The official start of his second White House bid comes 20 months before the November 2012 election.
"We've always known that lasting change wouldn't come quickly or easily. It never does," the Democrat said in an e-mail to supporters announcing his candidacy. "But as my administration and folks across the country fight to protect the progress we've made -- and make more -- we also need to begin mobilizing for 2012, long before the time comes for me to begin campaigning in earnest."
He told them he was filing the necessary paperwork with the Federal Election Commission, and directed them to his new campaign website where a launch video featured clips from supporters talking about their continued backing of the Democrat.
"I don't agree with Obama on everything but I respect him and I trust him," Ed from North Carolina says, delivering what's certain to become a key part of the president's pitch as he tries to re-energize liberals who have criticized some of his policies and independents who have fled from him in his first term.
Obama's announcement comes just weeks after the commander in chief directed U.S. military operations to a third major warfront, Libya, and days after the post-recession economy showed more signs of a rebound with a report that the still high unemployment rate had fallen to 8.8 percent.
Widely expected, the procedural step of launching a campaign was planned to coincide with the second fundraising quarter of the year. Filing paperwork will allow the president to begin raising money in earnest for what advisers hope will be a record-breaking haul of more than $1 billion for his campaign, which is based in Chicago. That begins this month; he's slated to visit major money venues of Chicago, New York and Los Angeles in the coming weeks.
Obama faces no primary challenger.
On the other side, the race for the GOP presidential nomination is just getting under way; more than a dozen Republicans are considering seeking the chance to challenge Obama in the next election. Only a few have taken the initial steps toward a candidacy, though several more are expected to this month. It's a wide open race with no clear front-runner.
Nevertheless, Obama said he's not taking anything for granted.
"We're doing this now because the politics we believe in does not start with expensive TV ads or extravaganzas, but with you -- with people organizing block-by-block, talking to neighbors, co-workers, and friends. And that kind of campaign takes time to build," he said in the e-mail.
"So even though I'm focused on the job you elected me to do, and the race may not reach full speed for a year or more, the work of laying the foundation for our campaign must start today," Obama added. He directed them to the new red, white and blue website for what he said was "a campaign that's farther-reaching, more focused, and more innovative than anything we've built before."
The website features Obama's new campaign logo -- 2012 with the rising sun in the background, a version of his 2008 campaign logo -- and announces that the campaign is kicking off.
The video is a montage of testimonials from a demographically diverse group of backers who intend to stay involved in this campaign.
"It needs to reflect the changes that we've seen in the last two-and-a-half years," says Katherine from Colorado. "Then we had an underdog senator. Nobody thought that he had a chance. And now he's the president."
Gladys from Nevada adds: "We're not leaving it up to chance" and "It's an election that we have to win."