But the expensive advertisements, paid for with so-called soft money, later led to calls for an investigation into Democratic fund-raising.

The full amount was later returned after questions were raised about Democratic fund-raising.

The investigators have been hampered because many of the important witnesses they would like to call, in regard to Democratic fund-raising, are unavailable.

Some fund-raisers say the investigations and criminal cases involving Republicans have created a climate that helps Democratic fund-raising.

Mr. Lieberman's record in support of business interests could help Democratic fund-raising for the fall campaign.

But in an election year in which Democratic fund-raising has reached unprecedented levels, the party was hardly a special occasion.

The witnesses are relatively minor figures in the inquiry, Republican investigators say, but they have important knowledge of improper Democratic fund-raising.

But the Republican action raises the same kinds of troubling questions that have swirled around Democratic fund-raising in the last year.

Mr. Clinton thanked donors, who were paying $10,000 and $25,000, for their support in the face of investigations into Democratic fund-raising.

The committee is also examining Democratic fund-raising.