Democratic leaders are tamping down on expectations for rapid change and trying to signal they will place a calm hand on the nation’s tiller.

“The country must be governed from the middle,” House Speaker Nancy Pelosi (D-Calif.) said Wednesday. Repeating themes from election night, she said she plans to emphasize “civility” and “fiscal responsibility.”

Yet, they face massive expectations for change and deep-seated fears of overreaching. But senior aides say they’ve learned from the mistakes of the past. Nearly every member of the current Democratic leadership in the House served through the 1992 election, when Bill Clinton was elected president.  Two years later, the GOP gained control of Congress.

More recently, they’ve watched Republicans go from complete dominance to minority status in the space of two elections.

“The difference is we have the benefit of experience in seeing what happens when you gain control,” said a senior Democratic aide. “I do not envision a scenario where we’d go off on an ideological mission in an undisciplined way.”

There are similar sentiments in the Senate.

“There is a wave of hope that swept the country ... not a mandate for any hope or ideology, but a mandate to get things done,” Senate Majority Leader Harry Reid (D-Nev.) said Wednesday morning on National Public Radio.

The Senate will provide a key test of the new Democratic agenda. While the House for the last two years has been able to pass most Democratic priorities, many could not get past GOP-led filibusters in the upper chamber.

Democrats had hoped to gain a 60-vote, filibuster-proof majority, but that now seems unrealistic. By Wednesday, they had 56 seats, including the chamber’s two independent senators. Four races are still outstanding: however, the Republican candidates leads in each.

That means to get legislation through, Democrats will have to reach across the aisle and pluck a few centrist Republicans to reach 60 votes.

Pelosi, in a rare exposition on Senate politics, noted that it’s more than Senate numbers that have changed. Senate Republicans often found themselves protecting President Bush from unpopular vetoes. Now that he’s gone, they’ll have different incentives.

“When the president vetoes something, the world knows, but when the Senate blocks something it’s not as well-known,” Pelosi said. Now, she said, senators might be more willing to negotiate “if they want to weigh in on the legislation.”

But an expanded majority, a Barack Obama administration and the “end of obstruction,” as some Democrats call it, mean they no longer get to blame failures on Bush. One of the thorniest issues will be passing legislation that is paid for without raising taxes, adhering to the party’s pay-as-you-go rules.

Now, Democrats face the prospect of fixing, or at least patching, big-ticket problems like the Alternative Minimum Tax with other taxes.

Pelosi gave great deference to the Blue Dog conservatives in her party for the past two years, as seen in the leadership allowing them to vote for Republican “motions to recommit” rather than enforcing strict party discipline. Republicans made little use of the tough votes they’d forced in the recent elections.

And there are some indications that despite the rhetoric, Pelosi is tacking to the left. Many see her hand in the effort by liberal Rep. Henry Waxman (D-Calif.) to oust House Energy and Commerce Chairman John Dingell (D-Mich.), an ally of the auto industry who generally takes a more pro-business approach to environmental regulation.

Along with new leadership openings that could be created by the departure of House Democratic Caucus Chairman Rahm Emanuel and others, the caucus will still have an opportunity to decide its direction for the future.