The battle over protecting the rights of citizen watchdogs who report suspected terrorist activity is about to erupt at City Hall and could become a key issue in the 2009 race to replace Mayor Bloomberg and even in the presidential election.

Recently, only one Democratic member of the New York City congressional delegation voted in favor of a measure approved in the House to protect people who report suspicious behavior relating to transportation security from the threat of lawsuits.

Rep. Anthony Weiner, who represents Brooklyn and Queens and is already running for mayor, backed the “John Doe” amendment, a reference to the unnamed defendants who told officials on a US Airways flight in Minneapolis last November that a group of imams was acting suspiciously. The imams sued the airline, airport officials, and the passengers who made the report.

An advertisement urging the Senate to pass the measure is appearing in the latest issue of City Hall, a free monthly publication. Another ad is expected to appear in the New York Post today or later this week, mayoral hopeful John Catsimatidis, who is paying for the ads, said. He is chairman and CEO of Red Apple Group and Gristedes.

Council Member Hiram Monserrate of Queens plans to introduce a resolution that would have the council press the Senate to approve the amendment, introduced by Rep. Peter King of Long Island.

“We congratulate Congressman Peter King for working hard to protect New Yorkers,” Mr. Catsimatidis, a Republican turned Democrat turned Republican, said. “If people get scared of turning in people, then I think it’s going to compromise New York security. And what I’m concerned about is New Yorkers.”

Mr. Catsimatidis said he took out the ads because he wants to put the issue “on the table” and hold elected officials accountable for their vote. He said Reps. Carolyn Maloney and Jerrold Nadler, Democrats of New York who voted against the amendment, are good friends of his and that he thinks the ad will let them know “maybe they should have looked at it twice.”

The resolution may not go far in the Democratic-controlled City Hall. All but three of the 50 current council members are Democrats, but Mr. Weiner’s support of the bill and an earlier statement by Mayor Bloomberg that people should be free report to law enforcement when they feel something’s wrong could prompt local officials to back the resolution.

Speaker Christine Quinn, who is widely believed to be planning a run for mayor, could not be reached for comment yesterday.

City Hall already has ties to the case that prompted the amendment. An attorney for the Council on American-Islamic Relations, Omar Mohammedi, serves as a Bloomberg administration appointee on the city’s Commission on Human Rights and is representing the six imams.

In the House, 105 Democrats voted in favor of the John Doe amendment and 121 voted against it. It passed March 27 on a vote of 304 to 121.

The amendment was added to the Rail and Public Transportation Security Act in the House. Mr. King said he or someone else would introduce the amendment to the Senate’s bill if the two sides of Congress as expected hold a conference on the legislation.

In a letter regarding the lawsuit, the executive director of the Council on American-Islamic Relations, Nihad Awad, wrote that the organization believes in upholding the Constitution and preventing violations of religious and civil rights.

“The only individuals against whom suit may be raised in this litigation are those who may have knowingly made false reports against the imams with the intent to discriminate against them,” he wrote. “When a person makes a false report with the intent to discriminate, he or she is not acting in good faith.”

Mr. King said it is appropriate for the City Council to speak out on the need to protect people who report suspicious behavior. Signs and public service announcements in the subway remind New Yorkers to report suspicious activity to authorities.

“This can be a wakeup call, a real reminder, a real signal to New Yorkers to be alert and be proactive,” Mr. King said. “It’s a call to the citizens to get involved and be involved, so yes, I think that city councils and state legislatures all over the country” should focus attention on the issue.

Mr. Monserrate said it is important for the council to take a position on the amendment.

“The city of New York, more than any place on this planet, was affected by terrorism the most on September 11,” he said. “It is an issue that is going to be debated, and rightfully so.”