THE decision by Nancy Kassebaum (R) of Kansas to retire from the Senate next year will mean the loss of another moderate voice in Congress and one of its most prominent women.
Her departure follows the recent announcement of other senior senators who have been regarded as brokers in the center, including Sam Nunn (D) of Georgia, Bennett Johnston (D) of Louisiana, and Bill Bradley (D) of New Jersey.
While few analysts expect the Democrats to pick up the Kassebaum seat, her retirement could further change the political dynamics of the upper chamber.
''Every time you have a conservative Democrat or a moderate Republican leave the Senate, it pushes their colleagues over to the extremes,'' says Charles Cook, editor of the Cook Political Report.
Ms. Kassebaum's decision to step down, announced Monday, came as no surprise. She was near the same announcement six years ago, when GOP elders, including then-Senate minority leader Bob Dole (R) of Kansas, urged her to run again and save the Senate seat from a Democratic win.
With Kassebaum's departure, there could be only seven female lawmakers left in the Senate. ''We will miss her, as she has been very supportive on women's issues as a moderating pro-choice voice in the Republican party,'' says Judy Newman, executive director of the National Women's Political Caucus.
Though political analysts say Kassebaum would be a shoo-in if she ran for a fourth term, they all but discount a Democrat from securing her seat. At her press conference on Monday, Kassebaum said she might have changed her mind if she thought the Democrats could win.
Still, it's not the GOP-Democrat balance that troubles some analysts, but the loss of a pragmatic voice. Mr. Cook says the trend of more politicians moving toward the ''margins'' leaves less chance for consensus. The moderates ''were the glue that held the institution together,'' and as their numbers decrease, he says, ''it's a real loss for the cause of centrism and the civility you used to see in the Senate.''
After a partisan brawl led to a budget impasse and a government shutdown, Kassebaum had some terse words for freshman Republicans in the House. Calling them the biggest stumbling block toward conciliation, she chided: ''You have to know how to pick your fights.''
The senator earned a reputation as a tough manager of the government's labor and social programs as chairwoman of the Senate Labor and Human Resources Committee. Even before she took the committee's helm and well before Republican efforts to balance the budget were in full swing, Kassebaum honed in on one of the last vestiges of the Democrats' Great Society programs of the 1960s.
She threatened to gut the Job Corps - a billion-dollar program designed to house, feed, and train wayward youth - if its administrators failed to clean up abuses. After a rigorous review period, including a series of hearings based on an inspector general's report, the committee endorsed continued funding for the program.
''People have to have the same reaction to this as they did when Colin Powell announced he would not run for president,'' says Norman Ornstein, senior fellow at the American Enterprise Institute. ''The same endearing qualities that make you want to vote for someone are the very qualities that keep them from doing so. There are no incentives for people in the center to stick around.''
Mr. Ornstein adds: ''I think the current political environment ground Nancy down.''