Pledging honesty in government, and a change in direction in Iraq, the first woman Speaker of the House of Representatives has vowed to seek common ground with opposition Republicans.
Nancy Pelosi, a liberal congresswoman from California, becomes the highest-ranking woman in the history of the U.S. government, second in the presidential line of succession after Vice President Dick Cheney.
After the traditional reading of the roll call of all 435 House members for which she was present, she made a ceremonial re-entry to a chamber packed with lawmakers amid thunderous applause and a standing ovation.
With her children and grandchildren looking on, Pelosi called her election a historic moment not only for the country, but for American women.
"It is a moment for which we have waited over 200 years! Never losing faith, we waited through the years of struggle to achieve our rights. But women weren't just waiting, women were working. Never losing faith we worked to redeem the promise of America, that all men, and women, are created equal."
Handing the gavel to Pelosi, Republican leader John Boehner also recognized the historic nature of the occasion, and sounded this theme of bipartisanship.
"Today, the Democratic party assumes the challenge and opportunity of majority power in the people's house. Republicans will hold the incoming majority accountable for its promises and its actions. But we also want to work with the incoming majority for the good of the nation that we were all elected to serve."
The Washington power shift reflects the outcome of the November congressional election, and has Democrats controlling the House by 233 to 202, with a razor thin margin of 51 to 49 seats in the Senate.
In coming weeks, the situation in Iraq will present challenges to both sides, as President Bush submits new military spending requests and his 2008 fiscal year budget.
Pelosi said the November election reflected Americans' rejection of an open-ended approach on Iraq, and their desire for a path leading to the withdrawal of U.S. forces from Iraq.
"Shortly, President Bush will address the nation on the subject of Iraq. It is the responsibility of the president to articulate a new plan for Iraq, that makes it clear to the Iraqis that they must defend their own streets and their own security, a plan that promotes stability in the region and a plan that allows us to responsibly redeploy our troops."
Pledges of bipartisanship were also heard from the Senate, where Democratic Majority Leader Harry Reid appeared with Republican Minority leader in that chamber, Mitch McConnell.
"Our efforts are going to be to work in a bipartisan basis, in an open fashion, to solve the problems of the American people." McCONNELL: "That we get past the level of partisanship that we have witnessed in recent years, and develop stronger personal relationships, as well as work across [the] party aisles."
Senator Reid was asked by reporters how pledges of bipartisanship will hold up amid debate over a way forward in Iraq.
"Iraq is where it is. The country is where it is. Iraq is an issue that we all need to work on, and we will work on that, and we will on that to the best of our ability in a bipartisan manner.
As early as next week, Democratic-controlled committees will focus on Iraq, with exhaustive probes expected into Bush administration Iraq policies.
The Democratic agenda, involving efforts to pass key legislation in the first 100 hours of House business, formally begins next week.
However, Democrats moved immediately to introduce rule changes governing how business is done in the House, sparking the first partisan exchanges and complaints from Republicans about majority intentions.
One of the Democrat's first key efforts is to impose new restrictions on the relationship between lawmakers and lobbyists.
This reflects Democrats' determination to draw a distinction between them and Republican rule, which was marked by influence-pedaling scandals, including one involving former lobbyist Jack Abramoff, whose name was linked to both Republicans and Democrats.
