Boxer is a California liberal whose daughter was once married to Hillary Clinton's brother. (The two are now divorced.) Cornyn is a white-haired conservative former judge from Texas who is one of George W. Bush's closest allies in the Senate.

While Cornyn and Boxer have publicly advocated their amendment to provide full disclosure on mortgages, neither is discussing the Dodd-Conrad case per se, as is customary.

Others members of the committee are Ken Salazar of Colorado and Mark Pryor of Arkansas, both Democrats and former state attorneys general; as well as two Republicans, Pat Roberts of Kansas and Johnny Isakson of Georgia.

The ethics panel has a range of tools at its disposal as it moves forward. It could investigate the matter and issue a letter dismissing the case. It could reprimand a senator or encourage the entire Senate to take up censure or dismissal.

Such moves are quite rare, however. The committee unanimously recommended the expulsion of Senator Robert Packwood of Oregon amid an investigation of sexual misconduct in 1995 after determining that he'd edited some documents and diaries sought by the panel and had refused to give over others. Packwood resigned before he could be ejected from the Senate.

In 2002, the panel "severely admonished" New Jersey Democrat Robert Torricelli for receiving illegal gifts from a campaign contributor. Torricelli, who was seeking reelection that year, dropped out of the race.

If history is any guide, the ethics panel could take several months to complete an investigation. The committee took 10 months to resolve a complaint about Louisiana Republican David Vitter after he was linked to a prostitution ring.

In that case, the committee concluded that the alleged transgression had occurred before Vitter had arrived in the Senate and thus was out of its jurisdiction.

While the panel moved more quickly on the matter of Senator Larry Craig and his arrest in an airport men's room, this is likely to be a slow probe, experts said.

First, the ethics panel must determine if the special mortgages that Dodd and Conrad received constitute a "gift" as narrowly defined by Senate ethics rules.

If it is proven that a V.I.P. mortgage meets the Senate's definition of a gift, then there's the matter of determining whether the two veteran Democrats knew or should have known that they were receiving such a benefit.

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