The Democrats registered a clear victory in both houses of Congress in the United States elections on Tuesday.
The party captured at least five Senate seats from their Republican rivals, increasing their majority in the 100-seat chamber.
Further gains were made in the House of Representatives, easily exceeding the 218 seats needed for a majority there.
All 435 seats in the House were up for election, and 35 Senate seats were available.
Analysts say winning control of both chambers should make it easier for President-elect Barack Obama to push through the legislation he wants.
In the House, the Democrats built on the 235 seats they had secured in the 2006 mid-term elections. Projections suggested the party would make a net gain of at least 17 seats.
In the Senate, the Democrats have 54 seats, compared with 40 for the Republicans. Two other seats are taken by independents who vote with the Democrats. Races in four states remain too close to call.
Despite their success, the Democrats appeared unlikely to win 60 Senate seats - the number required to prevent Republican senators from using procedural blocks such as filibustering to hold up legislation.
Voters also elected governors in 11 states and 153 proposals were to be decided in 36 states.
Voters in Colorado and South Dakota rejected initiatives that could have led to abortion bans.
Washington became the second state to allow people with terminal illnesses the option of doctor-assisted suicide, while Nebraska outlawed affirmative action.
Exit polls in California suggested a close race on a proposed constitutional amendment that would limit marriage to heterosexual couples. Thousands of gay couples have wed in the state since a court ruled in May that gay marriages could go ahead.