President Reagan liked to say that there is no limit to what one can accomplish if one doesn’t worry about who gets the credit, and nothing would make us happier than to see the Democratic majority in Congress succeed at leadership on issues where they have overlap with the Republicans. They certainly have a historic opportunity. They have ridden into power on a wave of discontent at the former Republican majority, but have not yet had to articulate a coherent platform. They find themselves in the position of leading without having made any firm promises during the campaign. It may prove fortuitous.

Certainly the 110th Congress has more freedom for creative thinking than most. Its lot looks even rosier when one considers how wide the Democrats’ tent is, embracing in the upper chamber everyone from Senator Lieberman, who could be mistaken for a liberal Republican, to Senator-elect Sanders, a self-described socialist. Their only two commitments to the electorate were to “fix” Iraq and to “fix” the economy. Hectoring President Bush proved a successful electioneering strategy, but it’s less clear that it would be a wise basis of governing, a point that the likely speaker, Mrs. Pelosi, seemed to fix on yesterday.

In respect of the war, the world will be watching the Democrats. Word of Secretary Rumsfeld’s resignation hit the television screens within minutes of Mrs. Pelosi’s assertion that new civilian leadership at the Pentagon would be required. Within an hour the president was seeking to avoid this being misinterpreted by either our enemies or our own fighting men, a good instinct when dealing with an opposition many of whose members sought to block additional funding for the war. Democrats have an opportunity to make clear whether they stand for retreat or victory. We’d like to think that the architects of the Democratic victory, Senator Schumer and Rep. Rahm Emanuel, both of whom have been hawkish on the war, understand this.

On the fiscal side, Democrats gained traction during the campaign by pointing up Republicans’ failure to control government spending. Now the Democrats have a chance to take the lead on reforming Social Security and Medicare, the biggest drivers of that spending. That’s not as far-fetched as it sounds. In the first year of President Bush’s administration, a bipartisan commission chaired by, on the Democratic side, Senator Moynihan and including Rep. Timothy Penny and the chief executive of Black Entertainment Television, Robert Johnson, both Democrats, issued a report on Social Security that included personal accounts among its recommendations. Another prominent Democrat, Senator Breaux, helped chair a presidential commission that has called for fundamental tax reform.

The most immediate opportunity for the Democrats is immigration reform. The inability to pass the kind of multipronged bill favored by Mr. Bush and many Democrats was one of the signal failures of the Republican Congress. So, for that matter, was the passage and then unwillingness to reform the Sarbanes-Oxley corporate governance law, and here too Democrats have a chance to effect positive change. Should the remaining hold-out Senate race in Virginia break their way, Mr. Schumer will be not only the hero of his caucus for having led the Democratic Senatorial Campaign Committee to victory but a leader of the movement for Sarbox reform.

In the midst of the Democratic win that may end up touching both chambers, the victory of Senator Lieberman in liberal Connecticut sounds a cautionary note for Democrats who might fall for the notion that the MoveOn.org-Daily Kos crowd holds the key to their future. Winning the Battle of Iraq, reining in entitlement spending, and striking a blow for immigration and business-regulation reform look like a surer path to a lasting majority. Democrats now have a unique opportunity to do so. So welcome to the fight.