Federal lobbyists have a clear preference who they want to win election to the Senate: the people who are already there.

A new study by the nonpartisan Center for Public Integrity shows that registered lobbyists overwhelmingly favor incumbents with their campaign contributions. In most Senate races this year, in fact, lobbyists have forked over not a single penny to challengers.

"When registered lobbyists dig into their wallets," the research group said, "incumbent senators almost always benefit."

The pattern is far from new. "This is the oldest story in American politics," said John Kenneth White, a political scientist at Catholic University of America. "Incumbents in congressional elections are increasingly like members of the Soviet Politburo -- they are almost impossible to dislodge. That's why lobbyists donate to them. It's a relatively safe bet."

The tendency to back the status quo is particularly pronounced in this election. Every senator who sought reelection this year -- 26 in all -- got money from lobbyists, the study reported. But only six of their challengers got any funds at all from registered lobbyists.

Of the $2.917 million that federally registered lobbyists gave to Senate incumbents and their challengers in the current election cycle, a mere 5.4 percent, or $157,000, went to challengers, the study found.

The average amount given by lobbyists to senators running for reelection was $95,000. The average amount lobbyists gave to the handful of challengers who received any donations from them was $26,000, data from the study showed.

The study examined the personal campaign contributions of more than 1,000 federally registered lobbyists from 1999 through September 2004.

The lobbyists gave to incumbents regardless of their party affiliation. In fact, Democrats running for reelection got the largest individual donations. Sens. Christopher J. Dodd (D-Conn.) and Harry M. Reid (D-Nev.) received about $190,000 each. Sen. Patrick J. Leahy (D-Vt.) collected $151,000 from lobbyists.

The recipient of the largest amount of lobbyists' largess was Senate Minority Leader Thomas A. Daschle (D-S.D.), who collected $259,000, the study said.

Republicans also got their share. The Republican incumbent who received the most lobbyist money was Sen. Arlen Specter (Pa.) -- $225,000, according to the study. Specter has been in a tight race with Rep. Joseph M. Hoeffel (D-Pa.).

Other major recipients of lobbyists' funds include Sen. Byron L. Dorgan (D-N.D.) with $147,000, Sens. Charles E. Schumer (D-N.Y.) and Richard C. Shelby (R-Ala.) with $137,000 each, and Sen. Patty Murray (D-Wash.) with $132,000.