On the night he won reelection in 1996, President Clinton proclaimed his desire to transcend partisanship and govern from a "vital American center." Yesterday, he appeared at a news conference to decry months of "reckless partisanship" that he said "threatens America's economic well-being and now our national security."

The Senate's brusque dismissal this week of a treaty that Clinton had identified as a critical foreign policy priority was a stark reminder of how bereft of vitality Washington's governing center has become.

On issues from entitlements to free trade, this year represents a repudiation of the centrist governing model in which Clinton once hoped to assemble majorities by challenging the orthodoxies of both parties.

The zeal with which Clinton made his case against Republicans yesterday, by contrast, reflected an entirely different strategy. Clinton has shown that he and his fellow Democrats can win the public relations battle by playing off the perceived intransigence of the GOP majority. Whatever the merits of this political calculation, however, the capital's atmosphere of confrontation is choking Clinton's hopes for ending his tenure with a string of large policy achievements.

An overhaul of Social Security is not happening. Nor is a comprehensive repair of the other big entitlement program, Medicare. Clinton's plan to give prescription drug coverage to seniors has been abandoned on Capitol Hill, and White House aides have begun crafting a fallback position aimed at eking out incremental reforms.

Republicans, meanwhile, are eviscerating many of Clinton's signature spending proposals and snubbing his ideas for education reform, such as providing federal aid to reduce class sizes and targeting poorly performing schools for extra help. And it is unlikely they will act on multibillion-dollar proposals he has laid out for raising taxes on cigarettes and giving tax credits to help low- and middle-income families with child care.

With 15 months left in his term, Clinton still holds some cards, as witnessed by last week's House victory on a bill expanding the rights of patients in health maintenance organizations. In recent years, moreover, the White House often has been able to make Republicans blink in the closing days of budget showdowns. But these flashes of strength have not altered the picture: Most of the expansive policy agenda Clinton laid out in his State of the Union address in January is languishing.

"Clinton's agenda has been just as centrist as he promised," said University of Illinois political scientist Paul J. Quirk. "The Congress is increasingly polarized and not receptive to that."

Republicans are thwarting Clinton's policy agenda, but it is not only them. Democrats have limited Clinton's flexibility -- and robbed him of legacy-building achievements -- on such issues as expanding his authority to negotiate "fast-track" trade agreements and reaching an accord admitting China into the World Trade Organization. Just last week, Clinton swallowed a transportation bill that included anti-clean air provisions he opposed, after Democrats told him they did not have the stomach for a veto fight.

The policy lassitude that has beset Washington results from two factors, according to many lawmakers. One is the hangover from last winter's impeachment trial, which left too many personal antagonisms to replicate bipartisan accords such as the 1997 balanced-budget agreement and the more grudging enactment of welfare reform in 1996. Second, many in both parties -- including House Democratic leaders and even some strategists on Clinton's team -- believe their political interests are better served through combat.

One person who does not believe in this strategy, for his party or himself, is Clinton, according to confidants. One former administration official who consults with Clinton said the president is dismayed by what he sees as the intransigence confronting him, a situation he blames on Republicans. "They choose to fight with him as a way of covering up their internal divisions, and their internal divisions are what make it impossible for them" to bargain with him on policy, said this adviser, describing Clinton's view of the GOP's approach.

But another former senior White House official, frustrated by Clinton's lack of policy progress, cited another obstacle: After Democrats came to Clinton's rescue in last year's scandal, he is much less inclined to run counter to their wishes, as he did on the budget in 1997 and on welfare in 1996. Some former aides said they have been dismayed by Clinton's passivity in accepting the political strategy of House Minority Leader Richard A. Gephardt (Mo.) and other Democratic leaders.

"It's horribly frustrating," said Sen. John Breaux (D-La.), a leader of his party's centrist wing, who had hoped this year would bring legislation putting Medicare on a sounder financial footing. While Clinton does not believe in the obstruction strategy of some House Democrats, Breaux said, "he does not want to step on the toes of members who think that."

A White House official involved in crafting Clinton's legislative strategy disputed this assessment. But he said there is no Republican willingness to work with Clinton, even though he is willing. "Tom DeLay has hijacked the Congress," this aide said, referring to the House majority whip from Texas, a bitter Clinton foe.

With the environment so hostile for dealmaking, Clinton is pursuing a different strategy to maintain his relevance. Rather than the comprehensive overhaul of Medicare Clinton had proposed, White House officials now say they hope to pass a scaled-down measure increasing funding for nursing homes and rural and teaching hospitals -- albeit with less money than many lawmakers want -- and imposing efficiency reforms, such as competitive bidding for medical supplies purchased with Medicare funds.

Clinton's announcement this week designating millions of acres of national forest off limits to roads and logging echoes the robust use of executive orders that helped him preserve clout in the months after the GOP won control of Congress in 1994.

Finally, aides note, Clinton has not given up trying to prod Democrats on issues where they have yet to embrace his brand of centrism. In a speech to the Democratic Leadership Council Wednesday night, for example, he laid out a case for how free trade can be expanded in ways that soften the economic dislocation labor unions warn against.

Mostly, though, Clinton will try to win showdowns with Republicans where he can, aides said. The next several weeks, White House aides say, will feature a barrage of White House rhetoric accusing Republicans of intransigence and extremism, especially on budget issues. The strategy is aimed at making Republicans give in or pay a political price.

It is probably an effective strategy -- but also a severely limited one, said George Edwards, a presidential scholar at Texas A&M University. "He's getting incremental and short-term gains, but he's not getting large bills," he said. If Clinton wanted to enact major policies in his limited time left in office, Edwards added, "he'd really have to focus on one or two things, and he'd have to make some concessions to the Republicans."