WASHINGTON —- 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.

With none of the fanfare that usually accompanies such campaign launches, the Georgian spoke to about 40 journalists and supporters in one of the smallest rooms at the National Press Club. He was flanked by his wife, Jeri, son Derek and a few aides, including Russ Verney, who once advised another third-party candidate, Ross Perot.

Barr, a former congressman from Cobb County, drew national attention when he pushed for impeaching President Bill 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.

He offered as proof his opposition to free schooling for the children of illegal immigrants. "If a person is illegally in this country, the taxpayers of this country and the government of this country owe them nothing," he said.

Barr's past ties with Libertarians have been tenuous, even in Georgia. "A significant number of Libertarians worked hard" to defeat him in his congressional race in 2002, said Daniel N. Adams, chairman of the state Libertarian Party. Since then, Barr has moved toward the small-government, individual freedom, Libertarian philosophy, said Adams, who came to Washington to stand with the newest presidential candidate.

Republicans have urged their former party member not to run for president, out of concern that it could hurt McCain in November, Barr said. He countered that those voting for him "would not likely fall into the category of people who would be enthused about voting for John McCain —- if such exists."

Barr's presidential ambitions have drawn especially sharp criticism from another prominent Georgia Republican, former House Speaker Newt Gingrich, who commented last week that Barr was "not an alternative" and that he had "zero hope of winning."

On Monday, Barr shot back: "I guess Newt would know. He apparently decided he didn't have a snowball's chance when he dropped out [of possible White House contention] a couple of months ago."

Barr said he was "very, very confident" that he would win the Libertarian nomination at the party's convention Memorial Day weekend.

Even so, Larry Sabato, political scientist at the University of Virginia, doubted that his third-party effort would have much impact unless Libertarians donate "many millions of dollars" for his campaign.

Otherwise, "he's going to get swallowed up in this massive general election campaign that's historic in nature," Sabato said of the anticipated match-up between McCain and Democratic Sen. Barack Obama, who is in line to become the first African-American nominee.

"He is more likely to be a footnote than anything else," Sabato said.

Barr said he was just beginning fund-raising and declined to announce his projected campaign budget. He called it "substantial."