It is time to take seriously the possibility that the Democrats will take control of the House of Representatives in the elections next month. The breaking of the Mark Foley scandal on the last day of the congressional session — who held onto the incriminating instant messages until this strategic delivery date? — put the Republican leadership on the defensive and changed the political landscape.

Speaker Dennis Hastert was right just to warn Mr. Foley off communicating with former pages when informed in 2005 of the “over friendly” e-mails that the St. Petersburg Times and Miami Herald independently concluded were so innocuous as to be unworthy of publication. But he erred in not bringing the Democratic member of the committee on pages into the process.

The House Ethics Committee, which seems to be taking a bipartisan approach, will draw its own conclusions. In any case, polls taken since Mr. Foley’s resignation suggest Republicans have taken a hit. And the traders at intrade.com, which publishes the odds on political contests, switched from putting their money on Republicans holding the House to Republicans losing control.

It seems unlikely that Democrats will win more seats than Republicans now have, which means that a Speaker Nancy Pelosi will face the tough challenge of holding enough of her caucus together to produce the 218 votes needed for a majority on seriously contested legislation. She and other Democrats have not had much practice at this, but neither did Republicans back in 1994.

Ms. Pelosi’s task will be complicated by bad blood among the leadership (as Newt Gingrich’s was). She is on bad terms with the current minority whip, Steny Hoyer, and she seems to have encouraged her ally John Murtha to declare he’d challenge Mr. Hoyer for the majority leadership. Also, there are more moderates in the Democratic Caucus (and likely to be more if they win the 15 seats they need for control) than in Republican ranks today.

Consider the fact that 34 House Democrats, most from districts carried by Mr. Bush in 2004, voted for the terrorist interrogation bill supported by George Bush and John McCain. That means a narrowly Democratic House is unlikely to act on presumptive Ways and Means Chairman Charles Rangel’s suggestion that it defund the military campaign in Iraq, as a 2-to-1 Democratic House voted to refuse funds for bailing out South Vietnam in 1975.

There were no American troops in Vietnam then, but there are in Iraq now, and the Armed Services Committee, with moderate Democrat Ike Skelton as chairman, is not going to pull the rug out from under them. But there will be pressure to draw down troop levels, and Iraqi leaders would be well advised to heed pressure, coming already from Republican war supporters like Christopher Shays, to get their army and police force operating more effectively. On domestic policy, a Democratic House will be able to obstruct but not to impose its own will. Mr. Rangel will surely see to it that no extensions of Bush tax cuts come out of Ways and Means, which means tax increases in outyears. Budget levels will be subject to fierce negotiations, as they were in the Clinton-Gingrich years. John Dingell as chairman of Energy and Commerce will deploy his considerable skills on regulatory issues, but these do not always split on party lines.The smart and canny Henry Waxman, as chairman of Government Reform, will undoubtedly launch a series of newsworthy investigations moments after being sworn in on January 3, 2007.

John Conyers, slated to be chairman of Judiciary, has been muting his earlier calls for the impeachment of President Bush, but he can be expected to move in that direction when he takes the gavel. There are few moderate Democrats on Judiciary, and Mr. Conyers could conceivably mobilize a majority to bring an impeachment resolution to the floor. Yet a Democratic Judiciary Committee is likely to be on President Bush’s side on immigration, and could produce a guestworker and legalization bill.

Of course, it’s not certain that there will be a Democratic House next year. Republicans will frame the election as a referendum on who can keep the nation safe, and they’ll point out that most House Democrats voted against the terrorist interrogation and National Security Agency surveillance bills. And Republicans have a superior turnout drive. Stay tuned.