The bitter partisan confrontation over civil rights legislation the Senate passed last week was an overdue explosion that poses problems for both President Bush and Democrats as they head toward this fall's congressional elections.

Despite generally harmonious relations over the past 18 months, tensions have been building as Democrats push for enactment of some of the most controversial, liberal parts of their agenda against stiff -- but often divided -- resistance from the White House and Senate Republicans.

Republicans suspect Democrats of trying to paint Bush into a corner, forcing him to choose either to bow to their demands or veto politically sensitive legislation such as the civil rights bill.

Democrats have equally strong suspicions that Republicans are delaying or obstructing the legislation to protect the president from political damage; some also suspect that Republicans are trying to undermine the record of the Democratic-controlled Congress.

The frustration spilled out on the Senate floor Tuesday and Wednesday when Democrats, aided by breakaway Republicans, imposed cloture to limit debate and speed passage of the rights bill, prompting angry complaints from Minority Leader Robert J. Dole (R-Kan.) that the GOP was being "gagged" and treated "like a bunch of bums."

There were strains within the two parties as well. Dole was angry at eight Republican moderates who bolted to support the Democrats on cloture. While the ordinarily divided Democrats rallied with only one exception behind Majority Leader George J. Mitchell (D-Maine), some moderate-to-conservative Democrats have been restive over the decidedly liberal tilt of some recent legislation, much of which has come out of the Labor and Human Resources Committee headed by Sen. Edward M. Kennedy (D-Mass.).

"The train hasn't wrecked, but it sure is rocking on the tracks," said Sen. Thad Cochran (Miss.), a member of the Republican leadership.

"I don't think this left any of us with a good taste in our mouths," said Sen. David L. Boren (D-Okla.), who voted for cloture and the civil rights bill despite misgivings about some of its provisions.

Several senators agreed that the Senate had come perilously close to shredding its fabric of "comity." But they also said the Senate is likely to heed the warning signs and avoid plunging deeper into paralyzing acrimony. "I think it actually helped to let off steam," said Sen. John C. Danforth (Mo.), one of the dissident Republicans who voted for cloture.

The "awful, mean-spirited atmosphere," as one Democrat described it, stemmed as much from the broader struggle over partisan leverage -- and eventual political rewards -- as it did from disputes over the sweep of proposed curbs on job discrimination in the civil rights bill.

Hanging in the balance are key elements of the Democratic agenda, from major social welfare proposals to a bitterly disputed campaign finance plan, along with the ability of Bush and the Republicans to win concessions or oppose the bills without adverse political consequences.

With a limited agenda of his own, Bush has created a vacuum that the Democrats have moved eagerly to fill, throwing the Republicans on the defensive.

But Republicans have powerful tools at their disposal, including more than enough members in both houses to sustain a veto if they remain united, which gives a strong advantage in bargaining to the president. Equally important are rules peculiar to the Senate that give a determined minority ample opportunities for resistance through delay or obstruction.

Delay becomes an especially potent weapon when Congress nears adjournment and stalling tactics can squeeze a bill off the calendar. This year, with budget-related bills expected to preoccupy both the Senate and House when they return in September, most non-budget legislation must be well on its way before Congress recesses for a month in early August.

Contending that Republicans are fighting their measures with a variety of stalls, Democrats have started filing debate-limiting cloture petitions, historically used mainly to end filibusters, just as the Republicans are beginning to clear their throats for debate.

If the Democrats can get 60 votes, which means picking up at least five Republicans if they suffer no defections themselves, cloture limits debate to 30 hours and puts tight constraints on amendments. Perhaps more important, "what it really gets you is the bargaining leverage that comes with demonstrating that the bill will eventually pass," as Boren put it.

When some Republicans objected to bringing up the civil rights bill last month, Mitchell filed a cloture petition for a vote to occur just before a joint meeting of Congress to hear African National Congress leader Nelson Mandela. Republicans recoiled at that prospect and agreed to let the bill come up in July.

By then negotiations with the White House were underway and proposed amendments to the bill were piling up, Mitchell noted in an interview. Mitchell said that when he could see no end to the negotiations or to the stack of amendments (172 at last count, including 143 from Republicans), he filed another cloture petition.

"Republicans have every right to delay on those measures with which they disagree," he said. "We obviously have every right to use procedures under the rules to overcome those delays."

Republicans, including many of those who supported the civil rights bill, regard Mitchell's tactics as heavy-handed, unfair and counterproductive in reaching compromise. They say Mitchell has exaggerated their delaying tactics and contend that some of their maneuvers are aimed at assuring that their own legislative alternatives are given fair consideration.

"My sense is that the resentment on our side is very real . . . about the premature efforts to cut off our ability to debate or present amendments," said Cochran.

Several other senators, including James M. Jeffords (R-Vt.), who cosponsored the civil rights bill with Kennedy, pointed to another source of concern on both sides of the aisle: the upcoming fight over campaign finance reform.

With the two parties still sharply divided over approaches to that legislation, an early cloture vote on the Democratic bill could put the Republicans once again in the painful position of having to vote "no" on speeding consideration of a popular issue. So Republicans were talking last week of trying to push for an agreement that would allow consideration of their alternative on favorable terms.

Mitchell said he has not decided whether to seek cloture on the campaign finance measure, and Boren, chief sponsor of the bill, has said he believes cloture should be held in reserve, while expressing concern that Republicans may be "dragging their feet" on the farm bill, now on the Senate floor, to delay the campaign finance bill.

In any case, the Senate is braced for a tough two or three weeks. "If we had a resolution for National Cookie Week, it would take two weeks to pass," lamented Sen. David Pryor (D-Ark.).