(AP) Unlike other candidates who have challenged Delaware's popular Republican congressman in recent elections, Michael Berg shouldn't have a problem with name recognition.

Since he spoke out two years ago about the death of his son, Nick, a 26-year-old contractor who was beheaded in Iraq, Berg has been interviewed, marched in anti-war protests and given speeches around the globe.

He's also been arrested about a half-dozen times for civil disobedience, most recently at the Pentagon while trying to get an audience with Defense Secretary Donald Rumsfeld.

"This midterm election is really a referendum on the war, it's a referendum on the Bush policies," said Berg, who believes the most urgent task facing the nation is to end U.S. military involvement in Iraq.

Berg, 61, is the only candidate for the Green Party's formal endorsement at its May convention.

Delaware's Green Party, which boasts about 600 members in an electorate of more than 547,000 registered voters, has never won a campaign. Berg has never run for office.

The incumbent, Republican Michael Castle, is the longest-serving U.S. House member in state history. Berg has raised a few thousand dollars; Castle has more than $1 million in his treasury.

"I'm not a politician; I'm a school teacher," said Berg, who retired from teaching in 2002. "There are times when it's really hard to do it, but I'm committed to it."

Berg said he had no notion of running for office when he moved to Delaware last spring. He just wanted to downsize from the four-bedroom house in Chester County, Pa., where he and his wife were besieged by media after their son's death, and transition to a more urban setting.

Once a registered Democrat, he switched affiliation to the Green Party after moving to Delaware, and party officials approached him late last summer about running.

"Some might whisper 'carpetbagger,' since he just came into the state in May," said Samuel Hoff, a political science professor at Delaware State University in Dover.

Dennis Spivack, a Wilmington attorney seeking the Democratic nomination, said simply that he understands Delaware better than Berg does.

"I don't see how you can come into a state and in just three to six months be truly representative," said Spivack, a Vietnam-era Navy veteran who agrees with Berg that the Iraq war was a mistake for which Castle bears part of the blame.

Hoff gives Castle's challengers little chance of winning but said general disillusionment with the Bush administration could reduce the incumbent's usually overwhelming margin by a few points.

"I think we have an interesting race which, on the face of it, looks like it's ganging up on Michael Castle in reference to the Iraq war," he said.

Other high-profile critics of the Iraq war seeking office include veteran Tammy Duckworth, a helicopter pilot who lost her legs in a grenade attack and narrowly won the Democratic congressional primary nomination for a suburban Chicago district.

About 10 veterans of the current fighting in Iraq and Afghanistan are candidates for Congress, all but one of them Democrats. They contend their battlefield experience will allow them to criticize the war without being written off as naive and weak on defense.

Berg's son, Nicholas, traveled to Iraq late in 2003 and again in 2004, hoping to find work repairing radio towers. He was last seen on April 10, 2004, when he checked out of a Baghdad hotel. Berg's headless body was found a month later on a Baghdad street, and his killers posted a videotape of his slaying on the Internet.

Michael Berg is angry at Bush for the war and what happened to his son, but he tries not to let it control him.

"You can't go around telling people that you stand for peace when you have hatred and anger inside yourself," said Berg. "If everyone votes for what they really believe, that's all I ask."

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On the Net:

Berg campaign: http://bergforcongress.us

Castle campaign: http://www.house.gov/castle/index.html