An eight-term Democratic congressman who supports the impeachment of Vice President Cheney, is a member of the Out of Iraq Caucus, and has a perfect voting record from groups that promote abortion rights, is the target of this political season’s most determined and well-funded effort by Democrats to oust one of their own party’s incumbents.

In a primary set for February 12, Rep. Albert Wynn, who represents parts of two Maryland counties adjacent to Washington, is facing an array of liberal organizations and unions intent on defeating him, including EMILY’s List, the League of Conservation Voters, MoveOn.org, the National Organization for Women, the national Service Employees International Union, the Sierra Club, and a local of the United Food & Commercial Workers.

Last week, SEIU’s political committee dropped $250,000 on television and radio ads against Mr. Wynn, a sum that amounts to about a quarter of the entire cost of the congressman’s re-election bid in 2006. On Thursday, MoveOn.org sent an e-mail message to its national membership calling Mr. Wynn “a right-wing Democrat” and asking members to contribute to a foundation executive making her second attempt at the Democratic Party nomination in the 4th district, Donna Edwards. On Friday, the Sierra Club reported that it spent about $17,000 on phone calls and consulting in aid of Ms. Edwards.

“We’ve been hearing from our members for a while that they’ve been disappointed in Al Wynn’s record on issues they care about the most,” a spokeswoman for the Service Employees, Stephanie Mueller, said. “Our members feel very strongly that the Iraq War was a mistake. We’re also concerned that he continues to do the bidding of banks and credit card companies as opposed to our members.”

The hard-hitting, union-funded TV ad attacking Mr. Wynn shows his face spinning on the wheels of a slot machine along with palm trees and dollar signs. “Wynn’s taken contributions from big oil companies, and he voted with Dick Cheney to give them huge tax breaks. He’s taken 15 luxury trips paid for by corporate lobbyists and voted eight times to raise his own salary,” the ad’s narrator says. “Al Wynn hit the jackpot all right, at our expense.” A graphic at the end of the ad suggests a vote for Ms. Edwards, but she is not depicted or mentioned in the narration.

Mr. Wynn’s critics point to a series of votes where he split with Democratic liberals. In 2002, he voted for the resolution authorizing the Iraq War. In 2005, he supported the White House-backed energy bill. In the same year, he voted for legislation to tighten the bankruptcy laws and opposed an amendment that would have negated a deal in which the Labor Department agreed to warn Wal-Mart in advance about child labor inspections.

In 2006, he opposed a “net neutrality” measure which would have barred Internet carriers from giving preference to certain traffic on their networks.

“This idea of being a corporate stooge, I don’t know where it comes from,” Mr. Wynn told The New York Sun yesterday. “They selected some things they don’t like, and they ignored other things I’ve done. That’s the business of politics.”

The congressman said he supported the energy bill because he secured a boost in annual authorized funding for low-income energy assistance to $5 billion from $2 billion. “I thought that was significant,” Mr. Wynn said. “My opponents would have liked to have $16 billion for poor people. If that had been on the table, I would have voted for it, but it wasn’t.”

Mr. Wynn said the bankruptcy legislation had protections for the poor and those with medical debts, but it was needed to address the problem of people of means using bankruptcy to escape their responsibilities. “The credit card companies and banks are going to survive either way, but small businesses are severely hurt when people just wipe out their debts if they have the ability to pay,” the congressman said.

On most of the votes, Mr. Wynn was in the company of prominent Democratic leaders, including some of the top presidential candidates. Senator Obama, whom the congressman endorsed yesterday, voted for the energy bill. Senator Clinton voted for the Iraq War measure. She and John Edwards also backed a version of the bankruptcy legislation in 2001.

In previous bids, Mr. Wynn had all but unanimous support from labor and many of the liberal groups. “He really has been dedicated to labor over a period of years,” the president of a Service Employees local standing by the congressman, Carnell Reed, said.

Ms. Edwards has compared her opponent to Senator Lieberman, who was pilloried by liberals and lost the Democratic primary in 2006, but managed to hold on to his seat by running as an independent. “On a range of issues, the congressman, his votes are similar to votes taken by Joe Lieberman, not the least of which is the war in Iraq,” she told the Sun yesterday.

“That’s ridiculous,” Mr. Wynn said. “I voted five times this year to limit the war, bring the troops home, and cut funding. I said in 2004, before the last election, that I thought the vote was a mistake.”

Ms. Edwards said Mr. Wynn recently tacked to the left, supporting measures like Mr. Cheney’s impeachment only after she surprised Mr. Wynn by coming within about 3% of defeating him in the 2006 race. “The congressman is like a weathervane, whichever way the wind is blowing, that’s the way he’s going. In this district, we want somebody who checks her gut,” the challenger said yesterday.

While Mr. Wynn’s donors include real estate developers and telecommunications executives, Ms. Edwards has drawn support from some who don’t typically tilt at Democratic incumbents, such as a think tank chief and former chief of staff to President Clinton, John Podesta, and an attorney and civil rights activist close to Mr. Clinton, Vernon Jordan. Connections from her work at the Arca Foundation, which is funded by heirs to the Reynolds tobacco fortune, helped her score donations from a smattering of Hollywood types such as Barbra Streisand.

The challenge to Mr. Wynn is something of a test for a coalition of groups demanding that Democratic lawmakers stick to liberal positions on consumer, environmental, and foreign policy issues. “Hopefully, this will serve notice on other members of Congress who may be out of step with their districts,” a veteran Democratic field organizer, Steven Rosenthal, said.