WASHINGTON — After the Reagan landslide of 1980 swept Bob Dole into the chairmanship of the Senate Finance Committee, Mr. Dole was not sure how to break the news to Russell B. Long, the Louisiana Democrat who had presided over the panel with unquestioned authority for 15 years.

“Who is going to tell Russell?” asked an anxious Mr. Dole.

That the incoming chairman of the Finance Committee was nervous about approaching the deposed head speaks volumes about the power vested in that position and the men who have held it.

The imminent departure of Max Baucus, Democrat of Montana, from both the Senate and the committee has put a new focus on the panel and the chairmanship, which has declined in stature and influence compared with the vital role it played in the Senate almost from the beginning. Without a shift in the power structure of the Senate, it appears likely the next committee leader will have only a fraction of the clout of those in the past.

In addition to Mr. Long, the esteemed chairmanship was the domain of such Senate forces as Lloyd Bentsen of Texas, Daniel Patrick Moynihan of New York, Mr. Dole of Kansas and Bob Packwood of Oregon (before his fall in a sexual misconduct scandal). Many other prominent Senate figures also held the gavel over the centuries.