The hard-fought Connecticut Senate race that has split Democrats in the Constitution State is also causing a rift between the American Civil Liberties Union’s national headquarters and its Connecticut chapter.

Leaders of the ACLU’s Connecticut affiliate have objected to an advertisement placed by the national ACLU that ran in the Hartford Courant late last month. The advertisement focused on Senator Lieberman, a Democrat who is running as an independent after losing a primary bid to an anti-war candidate, Ned Lamont.

“Will Senator Joe Lieberman pass this test on American values?” the ad asks. It features Mr. Lieberman’s photograph and office telephone number, along with warnings about pending legislation about detainees, torture, and wiretapping. “Tell Joe Lieberman his votes on this assault on American values will help determine your vote in November,” the ad says.

The chairman of the board of the Connecticut ACLU, Don Noel Jr., said he and several other board members felt it breached the organization’s pledge to stay out of electoral politics.

“It seemed to us to cross the line on partisanship, or to cross the line on not being nonpartisan,” Mr. Noel told The New York Sun yesterday. “I have complained and the national office has agreed with me. They have said they are sorry this might have been seen as partisan.”

A spokeswoman for the ACLU, Emily Whitfield, said the national group had agreed to make wider notification to local affiliates about similar ads in the future. However, she said there was no apology for the content of the ads, which she said ran in a dozen states and mentioned Democratic and Republican incumbents who might be persuaded to heed the organization’s concerns about antiterrorism legislation.

“There is not a sense here that the ads themselves were a mistake,” Ms. Whitfield said. She said the ads were reviewed and approved by an expert on campaign finance law.

In recent weeks, the ACLU’s national leadership has been under pressure from a dissident group, which has started a Web site, savetheaclu.org. The splinter group has blamed current ACLU leaders for a series of missteps, including an alleged effort to limit criticism of the ACLU by its own board members.

ACLU officials said the $200,000 ad campaign targeted both Republicans, including Senators DeWine and Voinovich of Ohio, and Democrats, such as Senator Ben Nelson of Nebraska and Rep. John Barrow of Georgia. “The point isn’t whether they are Democrats or Republicans or independents. The point is whether they were legislative targets,” Ms. Whitfield said. “That was the factor and the only factor.” Some of the targets of the ads are not facing re-election, she noted.

A former member of the Federal Election Commission, Scott Thomas, said the ads would not meet the standard to be considered an improper donation to a federal campaign. “My gut feeling is that that probably would not be deemed express advocacy,” Mr. Thomas said. “It does seem to be done in the context of a legislative battle.”

Asked about the reference to the November election, Mr. Thomas said,”Obviously, that is a veiled public threat, if you will, that does tie into the election, but I have a feeling you wouldn’t get four votes at the FEC for saying that’s express advocacy.”

Ms. Whitfield said the directors of local ACLU affiliates were notified about the ads. The director of the Georgia chapter, Debbie Seagraves, said she was untroubled by the ad the national group took out focusing on Mr. Barrow, who is locked in a tight race.

“To me, it’s a pretty straightforward issue ad,” Ms. Seagraves said. “I certainly don’t see it crossing a line. At no point did it say, ‘Pick this candidate over that candidate.'”

Mr. Thomas said the ACLU’s newspaper ads, which ran six weeks before the election, would likely have been illegal if run in on radio or television. “That’s kind of an interesting little quirk,” he said.

The Bipartisan Campaign Reform Act of 2002, also known as McCain-Feingold after its Senate sponsors, bars the use of union or corporate money for broadcast or cable ads that mention a candidate within 60 days of a general election. There is a limited exemption for advocacy groups, but the ACLU has said in court filings that it would not qualify.

The ACLU was one of several groups that challenged the constitutionality of the “electioneering communications” provision, precisely because it could limit the group’s advertising when legislative issues were being debated in the days before an election.

However, in 2003, the Supreme Court, in a 5-4 decision, upheld the pre-election restriction as constitutional.

Mr. Lieberman ultimately joined 12 other Democrats to vote in favor of the Military Commissions Act, which outlines procedures for trying detainees and places some restrictions on their access to federal courts. It passed the Senate, 65-34, and the House, 250-170. However, one of the specific provisions to which the ACLU objected in its ads, the use of secret evidence to convict detainees, was dropped during negotiations between Republican senators and the White House.

The ACLU’s ads also opposed legislation that would give President Bush new legal authority for wiretapping. It passed the House, 232-191, but was never brought to a vote in the Senate.