In April last year, the Environmental Protection Agency proposed badly needed policy “guidance” reminding the staff of the Army Corps of Engineers of their duty under the Clean Water Act to protect all bodies of water, large and small, from harmful development. The guidance was sent to the White House in February for final approval. There it has languished — another prisoner of election-year politics.

The 1972 law is designed to protect “the waters of the United States” from pollution. It requires anyone who wishes to dredge or fill a body of water — oil companies, developers, homeowners — to seek a permit from the Corps, which can stop destructive projects and mitigate the damage from others.

In recent years, two confusing Supreme Court decisions and wrongheaded guidance from the George W. Bush administration have created uncertainty about the bodies of water subject to regulation. The Corps has been increasingly applying its energies to protecting navigable waterways while ignoring thousands of miles of smaller streams and millions of acres of wetlands that are critical to the nation’s drinking water and aquatic ecosystems.

Environmentalists welcomed the guidance for its clarity and common sense: Small tributaries and wetlands with a hydrological connection to larger downstream waters would be covered. Irrigated areas, and farm ponds constructed for watering animals, would not. Not surprisingly, commercial and farming interests denounced the proposal as another “job-killing” regulation from the E.P.A. The White House, which has been under steady attack from House Republicans for supporting new clean air rules, appears eager to avoid another fight.