Don’t go crazy with the subpoenas.

It has been a long two years for Democrats, watching Republicans fail to check Trumpian excesses. Which means the new majority might be tempted to overreach and, like Mr. Gingrich’s professed revolutionaries, wind up coming across as more partisan and prurient than public-spirited. Investigations should be strategic and methodical and clearly in the public interest — for instance, looking into corruption among cabinet officials or waste of taxpayer dollars, rather than targeting more lascivious matters, like hush-money payments to former mistresses.

The trick will be finding the right balance in both tone and topic. Many Trump-hating Democrats might be in the mood for payback, but most Americans could easily be turned off by overt political games. And, let’s not forget, this is ultimately not about scoring points — Americans deserve better from their government.

The topic of Mr. Trump’s tax returns will be especially ticklish. The president’s refusal to follow his predecessors’ example and release such basic information raises too many questions about conflicts of interest to ignore. But things could get ugly. The chairman of the House Ways and Means Committee has the right to request a copy, at which point the White House must decide if it wants to mount a legal challenge. Democrats need to be ready to make a cogent case — persuasive to the public as well as the courts — for why Mr. Trump’s taxes are a matter of critical concern.

For now, Democratic representatives are making properly judicious noises about oversight. They are holding meetings among themselves to determine which issues should be priorities and how to avoid overlap among the committees. But once the new chairmen take over, the leadership will need a firm hand to minimize the wilding.

Groom the party’s next leaders.

The widespread assumption in Democratic circles is that Nancy Pelosi will reclaim the speaker’s gavel. Practically speaking, this may be for the best, but even Ms. Pelosi has begun referring to herself as a “transitional” leader.

After 16 years as the House Democratic leader , Ms. Pelosi comes with a truckload of baggage, and a growing contingent within her own party feels it is time for a generational overhaul. But the reality is that she has no obvious successor. Her two deputies, Steny Hoyer and Jim Clyburn, offer no fresher blood. Her presumed heir, Joseph Crowley, is on his way out the door, having lost his seat in the primary election. And while plenty of hungry younger members are eyeing the post, none is seen as having the mix of experience, savvy and grit needed to steer the caucus — which will feature a large, diverse freshman class — through what promises to be a wild two years.

Love her or hate her, nobody herds the cats better than Ms. Pelosi.

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