Washington ? In a day of ceremony and historic change, Rep. Nancy Pelosi became the nation’s first female House speaker on Thursday as Democrats eagerly took control of Congress for the final two years of President Bush’s term.

“The Democrats are back,” rejoiced Pelosi, and within hours, the House had cleared stricter new ethics rules on a vote of 430-1.

As is customary, the opening moments of the 110th Congress produced pledges of bipartisanship at both ends of the Capitol. Yet Pelosi and Senate Majority Leader Harry Reid signaled a new political order when they swiftly challenged Bush over the war in Iraq.

“No issue in our country is more important than finding an end to this intractable war,” said Reid, D-Nev. “Completing the mission in Iraq is the president’s job, and we will do everything in our power to ensure he fulfills it.” Bush is expected to announce a revised strategy next week for the war, which has claimed the lives of more than 3,000 members of the U.S. armed forces.

The two houses convened at the stroke of noon, under Democratic control together for the first time since 1994.

That meant a return to power for men long used to wielding it. Liberals such as Sen. Edward M. Kennedy of Massachusetts and Rep. John Dingell of Michigan are committee chairmen again, for example.

And it brought reduced circumstances to others – no one more so than Rep. Dennis Hastert, R-Ill., just a member of the ranks after eight tumultuous years as speaker.

By custom, lawmakers brought their children to opening ceremonies in the House, and Pelosi swept into the chamber accompanied by her grandchildren.

Formality reigned, as always, in the Senate, where Vice President Dick Cheney administered the oath of office to 33 new and newly re-elected senators.

Former President Clinton watched from the gallery as his wife, Sen. Hillary Rodham Clinton, was sworn in for a second term from New York.

In a chance encounter, he dodged questions about her presidential ambitions. “I would like not to talk about it today,” he said.

It fell to Rep. John Boehner of Ohio, the new House Republican leader, to hand the gavel – symbol of the speaker’s authority – to Pelosi. “Whether you’re a Republican, Democrat or an independent, this is a cause for celebration,” he said, noting her place in history.

But he also gave notice to the party she leads, adding, “Republicans will hold the incoming majority accountable for its promises, and its actions.”

Across the Capitol, Sen. Mitch McConnell of Kentucky took over as leader of minority Republicans, and said it was time to put an end to “a culture of partisanship over principle.” He said cooperation was clearly possible on minimum wage and lobbying bills, and he added that he hoped the issues of Social Security and immigration would also yield to compromise.

Reid said he was eager for cooperation, and he arranged for a rare closed-door meeting of all senators before the Senate convened to help set a more cordial tone.

While Thursday was set aside for ceremony and celebration in the Senate, the House plunged immediately into work on the agenda that Democrats campaigned on last fall.

Despite Republican procedural protests, the ethics changes drew the opposition of only one lawmaker, Rep. Dan Burton, R-Ind. Democrats said they marked a first step toward ending a “culture of corruption” that they said flourished under the GOP.

The changes expand restrictions on privately financed trips enjoyed by lawmakers, prohibit travel on corporate jets and require greater disclosure of earmarks, the pet projects inserted into legislation at the behest of individual lawmakers.

House members would still be allowed to take trips financed by foundations that seek to influence public opinion, but only if the ethics committee approves the travel in advance.

House Democrats have an ambitious agenda for the next few weeks. They have pledged to pass bills to raise the minimum wage, expand the opportunity for federally funded stem cell research, make Medicare prescription drugs cheaper, reduce the cost of student loans, implement anti-terror measures and reduce tax breaks enjoyed by the oil industry – all before Bush goes to the Capitol on Jan. 23 for his State of the Union address.