U.S. media reports are now projecting that the Democratic Party has won a close race in the state of Virginia, giving it majority control of the Senate.
In Tuesday's U.S. elections, the Democrats had already won control of the House of Representatives for the first time since 1994.
By Wednesday, the Democrats had already won 50 Senate seats. The focus is now on the southern U. S. state of Virginia, where Republican incumbent George Allen faced off against Democratic challenger Jim Webb.
Webb holds a lead of close to seven-thousand votes out of nearly two-point-four-million cast. Allen has not conceded defeat, with his campaign saying he will wait until a re-check of the vote counting is completed by local officials, probably on Thursday.
NBC and the Associated Press Wednesday evening declared Webb the winner. The AP reports about 50 percent of the ballots from Tuesday's election in Virginia have been rechecked and nearly all the absentee ballots have been counted.
All of the House's 435 seats were contested in Tuesday's elections. Democrats were voted into the majority with a gain of about 30 seats. Projections say Democrats won 229 House seats, Republicans 196.
Opinion polls showed that dissatisfaction with President Bush and his handling of the Iraq war drove many voters to cast their ballot for Democrats.
At the White House Wednesday, President Bush said he is disappointed with the election results, but called on both political parties to work together on issues of importance to Americans.
Congresswoman Nancy Pelosi, who is poised to become the first female Speaker of the House, has pledged partnership with congressional Republicans.
Senate Democratic leader Harry Reid said the message from the electorate is clear, and that Americans voted for change.
Tuesday's elections also included voting for governors in 36 states. Democrats made significant gains, giving them a majority of the top state offices for the first time in 12 years.
Several controversial issues also were on state ballots.
Voters in several states approved banning same-sex marriage. In South Dakota, a proposed ban on most abortions was rejected. And in Missouri, voters approved an amendment allowing stem cell research but banning human cloning.