That means control of the Senate is soon to switch from one party to the other, as Vermont Senator James Jeffords last week announced he would leave the GOP and become an independent soon after the tax bill was complete.
The ripple effects of that move are beginning to splash around Capitol Hill.
The Senate is now tied at 50 seats each for Republicans and Democrats, with Vice President Dick Cheney's tie-breaking vote giving the GOP nominal control. By switching parties, Jeffords gives the Democrats a 50-49-1 advantage, which means the Democrats now control key committees. Already, the Democrats are sorting out the spoils of the shift.
An aide to Senator Sen. Joseph Biden, D-Del., said Tuesday that Biden will assume the chairmanship of the Senate Foreign Relations Committee when the Democrats take control of the chamber next week.
Sen. Patrick Leahy, D-Vt., will preside over the Judiciary Committee, with jurisdiction over Mr. Bush's judicial nominees including any Supreme Court vacancies that occur.
The leadership changes will obviously have an impact on policy.
Sen. Tom Daschle, D-S.D., the incoming majority leader, signaled the shift in priorities when he disclosed plans Thursday to bring a patients' bill of rights to the floor shortly after the Memorial Day break.
Republicans said they would continue to press legislation the president favors. But stripped of the majority, effective on June 5, they can use their strength to check the Democrats, by filibuster if they choose.
Beyond the ability to place bills on the floor, Democrats will have one seat at three-way negotiations on final legislative compromises, something they lacked when Mr. Bush was dealing with a GOP-controlled House and Senate.
GOP leaders have tried to put the best face possible on the switch.
"When you're in the minority, sometimes I think it's easier to come together and be, you know, very aggressive in your tactics," said Sen. Trent Lott, of Mississippi, the GOP leader.
However, lawmakers in both parties said the likelihood of additional major tax relief had vanished. Mr. Bush's plans for missile defense may face setbacks. Agriculture policy may feel the effects of the switch, with Iowan Tom Harkin, one of Congress' most vocal critics of the 1996 "Freedom to Farm" law that loosened government controls on farmers and lowered price supports, poised to lead the Senate Agriculture Committee.
Sen. Frank Murkowski of Alaska, a supporter of oil drilling in the Arctic National Wildlife Refuge, will be out as head of the Energy Committee. Instead, Sen. Jeff Bingaman of New Mexico, likely to be more critical of the president's energy plan, will preside.
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With Jeffords' defection, the careful Washington watch of the health of 98-year-old Thurmond and his Republican compatriots such as 79-year-old Sen. Jesse Helms, R-N.C., will likely now fade along with the presumption that a Democratic takeover of the Senate could only be caused by the illness or death of a GOP senator.
Thurmond's standing as the longest-serving member of the majority party has made him Senate president pro tempore, a constitutional post of ceremonial powers that is third in line of succession for the presidency. That position now goes to a Democrat, 83-year-old Sen. Robert C. Byrd of West Virginia.
"The big change is the Senate Democrats will control the calendar," said Andrew Card, White House chief of staff. "It doesn't affect his (Mr. Bush's) policy agenda very much. It does affect how we have to work with Congress. The Senate Democrats will control their own agenda, rather than in consultation with the White House."
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