Declaring that the major party candidates have failed to offer voters real change, former Georgia Congressman Bob Barr jumped into the presidential race Monday under the Libertarian Party banner.

Barr, a former Republican who switched parties two years ago, said the federal government has grown too big, too costly and too intrusive in the years since the terrorist attacks on the United States on Sept. 11, 2001.

He said he is running "to let the American people know that they are going to have a choice" of a candidate who would shrink the size and scope of government and start bringing home U.S. troops from Iraq and other posts around the world.

Barr insisted that he was not trying to be a "spoiler" for presumed Republican nominee Sen. John McCain, whom he criticized as a "status quo" candidate.

Barr, a former congressman from suburban Atlanta, drew national attention when he pushed for impeaching President Clinton during the Monica Lewinsky sex scandal in 1998. He lost his House seat in 2002 after his district was redrawn and has since become an outspoken -- and sometimes controversial -- advocate for privacy and gun rights.

"I've never been called a compassionate conservative," Barr said Monday.