K Street's newest conglomerate is trying the bipartisan approach.

Interpublic Group, a New York holding company, is negotiating to acquire Barbour, Griffith & Rogers, one of Washington's largest Republican-leaning lobbying operations, according to sources.

If a deal is signed, Interpublic would own highly influential lobbying outfits on both sides of the political divide. Last month, the company spent roughly $70 million to acquire Cassidy Cos., a mini-empire that includes Democratic-inclined Cassidy & Associates, the city's largest lobbying company.

That raises a curious possibility: lobbyists who are cousins in the same corporate family warring with each other in Washington's power corridors. Arch rivals in the airline business, for instance, might find that the Washington guns they hired to fire at each other came from a single arsenal.

Officials at Interpublic declined to comment. Haley Barbour, a named partner at Barbour, Griffith and former chairman of the Republican National Committee, said: "We don't have an agreement with Interpublic or anybody. But when we do, we'll announce it."

With seven full-time lobbyists and $7.4 million in billings in 1998, Barbour, Griffith is the seventh-largest lobbying firm in Washington, according to data collected by the Center for Responsive Politics. That's less than half the size of the three largest lobbying companies in town, but Barbour, Griffith has excellent connections to Republican politicians through longtime links to Mississippi politics. Barbour and named partner Lanny Griffith hail from the Magnolia State and are considered close to Senate Majority Leader Trent Lott (R-Miss.).

The firm's connections have proven lucrative. Among Barbour, Griffith's clients are Microsoft Corp., Delta Air Lines Inc., DaimlerChrysler AG, BellSouth Corp. and all of the major tobacco companies. The firm also represents several influential trade associations, including the American Trucking Association and the U.S. Telephone Association.

It is unclear how close the two sides are to striking a deal, though the talks have been underway for weeks. Officials at Barbour, Griffith are said to be concerned with ensuring that the firm retains total autonomy. For starters, that means the latitude to sign clients as the firm pleases.

For Interpublic, whose stock is traded on the New York Stock Exchange, Barbour, Griffith offers another chance to expand a growing collection of lobbying, public relations and advertising subsidiaries. Interpublic's strategy is to use its companies to generate income for each other; a firm selling lobbying advice, for instance, could refer clients who might also need an advertising campaign.

The partners of Barbour, Griffith would benefit from a potential supply of new clients and would presumably sell out at a hefty premium. When Gerald Cassidy sold his firm, for instance, his stake was reportedly worth more than $10 million.

Whether corporate clients would fret about potential conflicts of interest if Interpublic becomes a two-party corporation is an open question. Many law firms have long cultivated ties to both Democrats and Republicans, but in the lobbying realm a firm typically must choose a side and stick with it. Tellingly, every penny of the $93,651 that Barbour, Griffith gave away in 1998 in campaign contributions went to Republicans.

"Who is going to trust them?" asked consumer activist and frequent K Street critic Ralph Nader. "Just because the companies would be organizationally at arm's length doesn't mean that operationally they'll be at arm's length."