WHEN the House of Representatives reconvenes in September, Republicans will have to scoot over to make room for another newcomer: Louisiana Rep. Billy Tauzin.
Last weekend, Congressman Tauzin became the fifth Democrat to switch to the GOP since last November's lopsided elections. He joins Sen. Ben Nighthorse Campbell of Colorado, Sen. Richard Shelby of Alabama, Rep. Greg Laughlin of Texas, and Georgia Rep. Nathan Deal.
While Tauzin's loss is another sign of the Democratic Party's deterioration, particularly in the South, his defection will probably not make a significant impact on legislation: Tauzin is one of two Democrats who voted for all 10 points of the Republican Contract With America.
The real questions are whether his defection will convince other conservative Democrats to switch affiliations, and whether the Democratic leadership will tilt rightward to prevent that from happening. So far, neither prospect seems likely.
In fact, some observers say Tauzin's absence might even help lift the downtrodden Democrats.
''In the long run, it will make both parties stronger,'' says Stephen Hess of the Washington-based Brookings Institution. ''Tauzin belongs in the Republican Party. By switching, he helps to sharpen the differences between parties, to make sure that both parties really stand for something.''
The recent spate of switching, Dr. Hess says, is just ''the tail end of the post-New Deal-era realignment.''
At a New Orleans press conference, Tauzin said the switch was ideological, not political. He says he gave the Democrats a chance to become a more ''centrist'' party, but that never happened. ''The liberal leadership of the Democratic Party, unfortunately, seems dedicated to preserving the status quo,'' he says.
Although the eight-term congressman had routinely blasted the Democrats, and his switch was rumored for months, House leaders had seemed lukewarm about disciplining him. Tauzin decided to switch, he says, when he was not assigned to a conference committee drafting a final version of a securities-litigation bill he crafted in 1990.
While Tauzin's departure drew barbs from some Democrats, it did not meet the level of venom that greeted the announcement of Mr. Laughlin last month. Shortly after the Texas congressman changed parties, the GOP leaders gave him a seat on the powerful Ways and Means Committee - a move Democrats condemned as political horse trading.