Senator Clinton’s former fund-raising chief, who faces four felony counts for causing the filing of false campaign finance reports, is seeking to have the indictment against him dismissed because federal prosecutors kept it secret for more than a year.

In motions filed with a federal judge in Los Angeles, attorneys for David Rosen argue that the government acted improperly when it persuaded a federal magistrate to seal the indictment after it was handed up in December 2003.

“Absent a fact-based, legitimate prosecutorial reason for the sealing, the indictment must be dismissed, even where the defendant has shown no prejudice,” wrote Mr. Rosen’s lead counsel, Paul Mark Sandler.

In the indictment, which was unsealed last month, Mr. Rosen is charged with failing to report in-kind contributions and producing a false invoice in connection with a star-studded August 2000 fund-raiser in California for Mrs. Clinton’s Senate campaign. He has pleaded not guilty.

Mr. Sandler noted that his client had been aware of the probe into his conduct since well before the indictment was returned.

“The government’s investigation of Rosen was common knowledge and there was no issue as to its ability to bring him into custody,” the lawyer wrote in a motion filed last week.

A spokesman for the Justice Department declined to comment for this story. The government’s initial motion to seal the indictment offered scant detail about the need to do so. It simply cited an ongoing investigation.

Mr. Sandler’s filing does not suggest why the government kept the indictment of Mr. Rosen under wraps. When asked in an interview to speculate on the possible reasons, the attorney said, “I probably shouldn’t.”

One lawyer familiar with the case said he suspects the indictment was sealed to avoid potential political fallout for President Bush in the lead-up to last November’s election.

“I can try to connect those dots,” said a Los Angeles attorney, George Bird. “Not knowing what they knew and what other investigation was going on, it just seems interesting in a case involving a political figure – one of the chief political figures facing them in the next election – they waited until after the election to release the indictment. It’s interesting the way they did that,” Mr. Bird said. He has been following the case because he formerly represented an organizer of the August 2000 fund-raiser, Aaron Tonken.

A source familiar with the investigation told The New York Sun that the 13-month delay in releasing the indictment of Mr. Rosen could have been the result of the government’s efforts to win the cooperation of another person who helped stage the August 2000 fund-raiser, Peter Paul.

Paul is facing federal stock fraud charges stemming from the demise of an Internet firm, Stan Lee Media. He was recently released on bail and has been in discussions with the government about a plea deal.

Mr. Rosen’s lawyers are also seeking to have the charges thrown out on other grounds, including the contention that it is not a crime to lie to the Federal Election Commission because it is not a part of the executive branch.

A formal response from the government to Mr. Rosen’s motions is due on Monday. A trial date is set for next month, but legal observers predict that the trial will not start before fall.