The Democrats have reportedly won the key Senate seat of Virginia with an upset victory that was needed to win the Senate.
If confirmed, the result would give the party complete domination of Capitol Hill for the first time since 1994.
Jim Webb's win over incumbent Senator George Allen gave Democrats their 51st seat in the 100-seat Senate, an astonishing turnabout at the hands of voters unhappy with Republican scandal and unabated violence in Iraq.
Mr Allen was the sixth Republican incumbent senator defeated in yesterday's elections.
The Senate had teetered at 50 Democrats, 49 Republicans for most today, with Virginia hanging in the balance.
Senator Webb's victory ended Republican hopes of eking out a 50-50 split, with Vice President Dick Cheney wielding tie-breaking authority.
The Associated Press contacted election officials in all 134 localities where voting occurred, obtaining updated numbers today.
About half the localities said they had completed their post-election canvassing and nearly all had counted outstanding absentees. Most were expected to be finished by Friday.
Recount looms
The new AP count showed Webb with 1,172,538 votes and Allen with 1,165,302, a difference of 7,236.
However if the final margin is less than one percent, either candidate can call for a recount, which would take weeks.
Virginia has had two statewide vote recounts in modern history, but both resulted in vote changes of no more than a few hundred votes.
An adviser to Mr Allen, speaking on condition of anonymity because his boss had not formally decided to end the campaign, said the senator wanted to wait until most of canvassing was completed before announcing his decision, possibly by tomorrow evening.
The adviser said that Mr Allen was disinclined to request a recount if the final vote spread was similar to that of election night.