Sen. Bob Kerrey (D-Neb.) announced yesterday that he will not seek reelection this fall, concluding a 12-year career of feisty independence on Capitol Hill and dealing a new blow to the Democrats' already slim prospects of winning control of the Senate.

After nearly two weeks of public and private soul-searching over whether to run for a third term, the 56-year-old lawmaker, heavily decorated Vietnam War veteran, millionaire businessman, former governor and 1992 presidential candidate said it was time for him to return to private life.

Flanked by his two grown children at a news conference in Omaha, Kerrey said he wrestled with the decision until late Wednesday night, even to the point of preparing two speeches reflecting different decisions.

He said he liked the speech anticipating another six years in the Senate better but found that, in the end, it came down to "more a case of wanting to get back to private life than stay in public life."

In typically unconventional Kerrey language, he described it as a "deeply personal decision" and added: "I have a spiritual, interpersonal and creative cistern that needs to be filled back up. . . . It's a little dry right now."

Kerrey's decision will complicate the already uphill battle Democrats face to win back the Senate, now controlled 55-45 by the Republicans. Democrats have improved their chances of reclaiming the House, in large measure by persuading many members to put off retirement or plans to seek higher office.

In the Senate, by contrast, Democratic efforts to pick up seats have become more difficult because of retirements, including Daniel Patrick Moynihan (N.Y.), Frank R. Lautenberg (N.J.) and Richard H. Bryan (Nev.), as well as Kerrey. The only Republican incumbent not running for reelection right now is Connie Mack (Fla.).

Although Nebraska leans Republican, Kerrey was regarded as a virtual shoo-in for reelection because of his personal popularity in the state. But the race is now seen as among the most competitive in the country, with Republicans probably having an edge.

With a sharp intellect, acerbic wit and often contrarian approach to legislative issues, Kerrey often baffled his colleagues and sometimes caused heartburn among Democrats as well as Republicans. Among them was President Clinton, whom he challenged for the Democratic nomination in 1992 and later criticized for lack of budgetary boldness. Before Clinton's impeachment, Kerrey called Clinton "an unusually good liar." But, like other Senate Democrats, he voted for Clinton's acquittal.

More of a centrist than many of his Democratic colleagues, Kerrey has some conservative fiscal instincts and worked aggressively for overhaul of costly benefit entitlement programs. But he was also a loyalist on many issues and led the party's campaign committee when Democrats blocked GOP efforts in 1998 to reach a 60-vote majority--enough to block Democratic delaying tactics.

Kerrey, a Vietnam veteran who lost part of a leg in a war he later opposed, is remembered by some for passionately evoking patriotic themes in opposing a constitutional amendment to ban flag burning--a speech that appeared to give others ample political cover to oppose the proposal.

Despite their sometimes difficult relations, Clinton led the parade of politicians who lamented Kerrey's decision, saying the senator was "always willing to be on the cutting edge of change" and hailing him for "pivotal leadership to turn our economy around by getting rid of the deficit."

Until two weeks ago, Kerrey had been considered almost certain to run for reelection. But after rumors surfaced recently that he was under consideration for the presidency of the New School University in New York City, he confirmed that he was thinking of leaving the Senate.

Kerrey consulted widely with colleagues and friends, and some, such as Sen. Tom Harkin (D-Iowa), tried to talk him out of retiring. He spoke several times with Minority Leader Thomas A. Daschle (D-S.D.), who said yesterday that he regretted but respected Kerrey's decision.

Kerrey said yesterday that he has not been offered the New School job but acknowledged that the option got him thinking about doing something new. He is looking at a variety of options in private life, but he has not ruled out a return to politics at some point.

Former Nebraska Gov. Ben Nelson, who was defeated in a run for the Senate in 1996, is regarded as a strong possibility to run for Kerrey's seat as a Democrat. Rep. Doug Bereuter (R) ruled himself out yesterday, but two other Republicans, state attorney general Don Stenberg and physician Elliott Rustad, have already announced and several other Republicans are looking at the race, including former University of Nebraska football coach Tom Osborne.