President-electis facing a Congress with bulked-up Democratic majorities in both the House and Senate to put much of his agenda into law.
Obama will inherit a Congress with Democratic House and Senate majorities comparable to those enjoyed by President Clinton when the party last controlled both Congress and the White House in 1992. While Democrats are eager to churn out the new president's legislative programs, they're also anxious to avoid the electoral wipeout that swept them from power in the 1994 congressional elections.
That's one reason top leaders like House Speaker Nancy Pelosi promise not to lurch to the left and give in to pent-up demands from party liberals.
"The country must be governed from the middle," Pelosi, D-Calif., told reporters Wednesday. "You have to bring people together to reach consensus on solutions that are sustainable and acceptable to the American people."
One of the complications for Pelosi and Obama is the demise of GOP moderates like Rep. Christopher Shays, R-Conn., who lost his re-election bid.
"Never in modern day history has the Republican Party been more bereft of a center," said former Rep. Jim Leach, R-Iowa. "So the center has to come from the Democratic Party."
There are other reasons too, such as a coalition of Republicans and a few conservative Democrats in the Senate. In the House, a big bloc of moderate-to-conservative "Blue Dog" Democrats also could put the brakes on overreaching by Obama and allies like Pelosi and Senate Majority Leader Harry Reid, D-Nev.
But after 14 years of either a GOP-dominated Congress or a Republican president, Democratic Party regulars are under intense pressure to deliver on an agenda they've been promising long before Obama announced his bid for the White House.
"I'm not worried about overreaching," said Rep. Jim McGovern, D-Mass. "I'm worried about being too timid and too cautious, and not stepping up to the plate and doing what we promised we would do."
Added Sen. Sherrod Brown, D-Ohio, "This election ushered in the next progressive era for our nation. From health care to trade to education, progressive values will now be the priority in Washington. It's time to get to work."
House Majority Leader Steny Hoyer, D-Md., countered that Democrats would impose "self-discipline" because so many House newcomers come from conservative-leaning districts.
"If we focus on the core issues of jobs, of health care, of education, of the environment ... I think we will not make mistakes," Hoyer said.
Inside Pelosi's caucus of House Democrats, whose numbers will swell to at least 254 from 235 now, some tensions are already apparent.
Rep. Henry Waxman, D-Calif., a liberal Pelosi ally, launched a bid to challenge 82-year-old Rep. John Dingell, D-Mich., for the chairmanship of the influential House Energy and Commerce Committee, and take the lead on issues like global warming, energy and health care. Dingell is a staunch protector of Detroit automakers, and his battles with Waxman over clean air laws date to the Reagan administration.
Dingell, who has either chaired the committee or been its top Democrat since 1981, was "mounting a full-out war" to save his chairmanship, a top adviser said Wednesday.
Republicans, too, are facing tensions and a shake-up of party leaders in the wake of Tuesday's disappointing election results.
Rep. Eric Cantor of Virginia launched a bid to become GOP whip, the No. 2 post, while Rep. Jeb Hensarling, R-Texas, is seeking to replace Rep. Adam Putnam of Florida as the third-ranking Republican in the House. Putnam announced he would step down after Tuesday's losses for Republicans. The current whip, Rep. Roy Blunt of Missouri, was considering his options but did not immediately announce a bid to keep his job, a sign that he'll likely step aside.
Both Cantor and Hensarling are more conservative than the lawmakers they're seeking to replace, leading some Republicans to grumble that the party was moving to the right when it should be reaching toward the center if it is to regain its majority. House Minority Leader John Boehner of Ohio said he would seek to keep his post.
Leon Panetta, a former House Democrat and White House chief of staff for Clinton, said Obama "has to make an effort at bipartisan cooperation, which means that he has to reach out to the Republicans and see whether or not they're willing to cooperate on some issues," like education and immigration. He added that Obama will need to develop coalitions on issues that divide Democrats.
Shake-ups also are possible in the Senate, where Democrats have increased their effective majority to at least 56 seats in the 100-member chamber. Sen. Joe Lieberman of Connecticut, one of two independents who align with Democrats, is threatened with the loss of his chairmanship of the Homeland Security and Government Affairs Committee as payback for actively supporting the presidential bid of Republican Sen. John McCain. Reid, the majority leader, said he would meet with Lieberman later in the week to discuss the matter.
"Now that the election is over, it is time to put partisan considerations aside and come together as a nation to solve the difficult challenges we face and make our blessed land stronger and safer," Lieberman said in a written statement. He had harshly criticized Obama in a speech at the GOP nominating convention in September.
Then there's the game of musical chairs in the Senate that has to be played because of the departures of Obama and Vice President-elect Joe Biden to the White House. Illinois Gov. Rod Blagojevich, a Democrat, will appoint someone to fill out the remaining two years of Obama's term. Speculation has focused on Chicago Reps. Jesse Jackson Jr. and Danny Davis, along with Rep. Jan Schakowsky.
Biden's departure opens up not only his seat - he won a seventh term Tuesday - but also the prestigious chairmanship of the Senate Foreign Relations Committee. Delaware's departing Democratic governor, Ruth Ann Minner, likely will name a successor to serve until the end of next year, when a special election will be held to fill the remaining four years. Speculation surrounds Lt. Gov. John Carney and Biden's son Beau, who is Delaware's first-term attorney general.
Sen. John Kerry, D-Mass., could be in line to fill the Foreign Relations post, depending on whether Sen. Christopher Dodd, D-Conn., decides to stay on as chairman of the Senate Banking Committee to deal with the financial meltdown.
Democrats have added at least five seats in the Senate, to bring their numbers to 56 - for now. But three GOP-held seats - in Oregon, Alaska and Minnesota - have yet to be decided. A fourth still-disputed Senate seat now held by a Republican incumbent will be settled by a Dec. 2 runoff in Georgia.