The election of members of a terrorist group, Hamas, to lead the Palestinian Arab government may be undermining attempts to prosecute the organization’s alleged operatives in America.

On Friday, a federal judge in Chicago ruled that defense attorneys for two men accused of handling Hamas’s financial affairs here, Abdelhaleem Ashqar and Muhammad Salah, may tell jurors about the vote in January that gave the group a majority in the Palestinian Arab parliament.

Judge Amy St. Eve said she agreed with lawyers for Mr. Ashqar that the electoral victory “is relevant because it demonstrates that Hamas engages in legitimate political and social measures.” The judge also said Hamas’s role in the Palestinian Arab government could support Mr. Ashqar’s contention “that the money he donated went to the legitimate purpose of consensus building and campaigning, rather than terrorist activities.”

“This gives Hamas a little bit more legitimacy in front of the jury,” a lawyer for Mr. Ashqar, William Moffitt, said in an interview yesterday. “Obviously, part of our defense is that you can be a member of Hamas, as long as you’re not supporting the violent side.”

Prosecutors argued that the vote was irrelevant because the charges against both men relate to alleged acts that took place long before this year’s Palestinian Arab elections.

In a separate and unexpected development Friday, the government dismissed one of the key counts in the case, which is set to go to trial on October 12.

At a hearing where defense lawyers were demanding information on payments to an informant, a prosecutor, Joseph Ferguson, quietly indicated that the government planned to drop a charge of material support of terrorism against Mr. Salah, according to the Associated Press.

“We said, ‘What?’ and the judge said, ‘What?'” a lawyer for Mr. Salah, Michael Deutsch, told The New York Sun. The move left racketeering conspiracy and obstruction of justice charges pending against Mr. Salah and his co-defendant, Mr. Ashqar, who was not charged in the dismissed count.

“It really is a change in the nature of the whole case,” Mr. Deutsch said.

Prosecutors did not explain their decision in court. A spokesman for the prosecution, Randall Samborn, said he could not elaborate on the move.

The prosecution action essentially dropped all the claims in the indictment that in 1999 Mr. Salah dispatched an agent to the West Bank and Jerusalem to provide funds to the family of an imprisoned Hamas leader and to scout out locations for possible bombings and kidnappings.

Mr. Salah’s lawyers called the alleged agent, Jack Mustafa, a “liar” who provided false information on several occasions while serving as an FBI informant. Before Friday’s development, the defense team had asked the judge to bar Mr. Mustafa’s testimony as inherently unreliable.

The dismissal leaves prosecutors with what could be regarded as a stale case against Mr. Salah, who spent between 1993 and 1997 in Israeli jails and admitted to carrying money for Hamas. He contends that his admissions were the product of torture, but Israeli officials deny that any mistreatment took place.

Prosecutors contend that between 1989 and 1993, Mr. Salah traveled the globe, meeting and giving funds to high-level Hamas officials, including a so-called military planner for the group. However, the American government did not place Hamas on an official list of terrorist organizations until 1995.

Mr. Deutsch said there is now no charge that Mr. Salah did “anything of substance” for Hamas after it was designated as a terrorist group. He is still charged with obstructing justice in 2001 for allegedly submitting false answers in connection with a lawsuit brought by the family of an American teenager, David Boim, killed in a Hamas attack on a West Bank bus stop in 1997.

One additional headache prosecutors are facing is a decision by President Bush and other top officials to use the phrase “the militant wing of Hamas” to describe those responsible for recent attacks on Israeli soldiers.

Mr. Bush used that or similar phrasing on at least five occasions in July. The American ambassador to the United Nations, John Bolton, also used the phrase as part of what seemed to be a concerted attempt to split Hamas and to encourage more moderate members of the group to soften their line toward Israel.

However, the rhetoric may also bolster defense attorneys’ claims that their clients’ actions for Hamas were strictly for the group’s charitable and political efforts, and not for terrorism.

“It’s very helpful,” Mr. Ashqar’s lawyer, Mr. Moffitt, said.

“It really reinforces what we’ve been saying all along,” Mr. Deutsch said. “Hamas does a lot of legal stuff and a lot of illegal stuff. … The government’s position in our case is that Hamas is a unitary organization and everyone’s part of it.”