WASHINGTON - After a marathon effort by its many long-time supporters and an ultimate showing of bipartisanship in Congress, the Indian Health Care Improvement Act reauthorization bill passed the Senate Feb. 26 by a vote of 83 in favor and 10 opposed.

The bill, at least eight years in the making and often a subject of exceptional controversy over issues that ranged from the narrowly medical and technical field to broad constitutional questions, provides up to $16 billion for Indian health care through the next five fiscal years. Just as importantly to its backers among tribes, the bill updates the responsiveness of tribes and the IHS in numerous priority areas, including cancer screening, diabetes treatment, disease prevention, youth suicide and mental health intervention, traditional approaches to healing and in-home health care, recruitment to the health profession as practiced in Indian country, and Medicare and Medicaid reimbursement.

The comfortable margin gave little indication of the hard-fought struggle to get the bill over a host of hurdles on its way to the vote for final passage. Approximately 40 amendments received some degree of consideration, though not all of them were offered, according to Heather Dawn Thompson, director of government affairs for the National Congress of American Indians.

None of the eventual amendments that attached to the bill are so-called ''poison pill'' amendments that would damage its chances of becoming law, she added.

Late in the process, a so-called substitute version of the original, engineered by the bill's managers on the Senate floor, Sens. Byron Dorgan, D-N.D., and Lisa Murkowski, R-Alaska, addressed wage issues that had led to a veto threat by the Bush administration, said Barry Piatt, communications director for Dorgan on the Senate Committee on Indian Affairs, which Dorgan chairs (Murkowski is the committee's ranking Republican). ''As things stand now,'' Piatt said Feb. 25, ''we expect the bill to pass ... in a version we expect the White House will sign.''

Following final passage, Sen. Mike Enzi, R-Wyo., one of the bill's prominent GOP backers (along with Murkowski and Sens. Jon Kyl and John McCain of Arizona) as ranking member of the Health, Education, Labor and Pensions Committee, also said he expects President Bush will sign the bill.

''It's our understanding that there is no longer a veto threat on this bill,'' Thompson added.

Prior to final passage, the Senate considered four amendments, adopting two of them. Sen. David Vitter, R-La., offered one banning any taxpayer funds from supporting abortion under the bill. Dorgan agreed with the stated goal, but called the amendment ''unnecessary'' and in part (he referred to Section 2) incomprehensible. To Vitter's plea for further discussion, Dorgan said a committee hearing would have been the place for that. The ''rider'' amendment passed by a vote of 52 - 42.

The final successful amendment to the bill came from Sen. Gordon Smith, R-Ore. It called on the IHS to engage in government-to-government relations ''with all tribes, not just a few,'' by developing a formula for construction funding that is fair across all IHS regions, rather than concentrating on larger tribes.

''He's raising the right question,'' Dorgan said of Smith, a regular voice in behalf of Indian-specific issues. ''I just happen to believe it's the wrong answer,'' he added, because tribes that have lingered for years on the IHS priority list for health facility construction, and are now at the top of it, could be kept waiting by another funding formula. After the 56 - 38 approval of the Smith amendment, Thompson noted that it doesn't mandate a change in the current IHS formula for construction funding, but permits it. ''So there's a lot left to talk about.''

Much, too, remains to be said about the cooperation, the bipartisanship, the commitments held to be nothing short of heroic, that have gone into getting the bill this far in the legislative process.

But for now the bill, S. 1200 in the Senate, awaits action in the House of Representatives. An identical version of it has passed the House Resources Committee and is now before the Energy and Commerce Committee. Thompson said that because so much work has already gone into the fine points of S. 1200, there is some hope the third committee of jurisdiction in the House, Ways and Means, may expedite its own consideration of the bill.