George Bush's Republican Party has won control of the US senate.
It means the opposition Democrats have little power left in Washington.
By winning their 50th seat with a victory in Missouri the Republicans have ensured Vice President Dick Cheney will have to cast his tie-breaking votes.
The win will give President Bush's legislative agenda a major boost in the next Congress.
The triumph came on a night that began with Democrats clinging to a one-seat margin, and it meant they will have to relinquish the majority they have held since Vermont Senator James Jeffords abandoned the Republicans in June 2001.
With at least 47 senators, Democrats will still be able to use filibusters - procedural delays - to kill Republican initiatives because such roadblocks need only 41 votes to succeed.
Even so, the Republicans capture of the Senate seemed likely to deny Democrats of their major remaining source of power. Republicans already control the White House and they recaptured their House majority Wednesday.
"It's been a very successful night for the Republican Party, for the president of the United States and for the country at large," said Sen Bill Frist, who headed the Republican 's Senate election effort.
His Democratic counterpart, Sen Patty Murray was predictably less effusive.
"We knew we had an uphill battle to begin with and I think it played out tonight."