(CBS/AP)  

President Obama formally launched his re-election campaign Monday, urging grass-roots supporters central to his first campaign to mobilize again to protect the change he's brought in his first term.

 

The official start of his second White House bid comes 20 months before the November 2012 election.

 

"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," Obama said in an e-mail to supporters.

 

He told them he was filing the necessary paperwork with the Federal Election Commission, and directed them to his newcampaign website where a launch video featured snippets from supporters testifying about their continued backing of the Democrat.