U.S. media reporting of the war in Iraq fell sharply in the second quarter of 2007, largely due to a drop in coverage of the Washington-based policy debate, a study released Monday said.

Taken together, the war's three major story lines -- the U.S. policy debate, events in Iraq and their impact on the U.S. homefront -- slipped roughly a third, to 15 percent of an index of total news coverage, down from 22 percent in the first three months of the year.

The study by the Project for Excellence in Journalism examined 18,010 stories that appeared between April 1 and June 29. Its "News Coverage Index" encompasses 48 outlets, including newspapers, radio, online, cable and network television.

The project is a research group studying and evaluating press performance. It describes itself as nonpartisan, nonideological and nonpolitical. The index is designed as an audit of a broad cross-section of U.S. news media.

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The 2008 presidential campaign -- with its crowded field for the Democratic and Republican party nominations -- emerged as the top story in U.S. media in the second quarter, overtaking the Iraq policy debate, the biggest thread of the three Iraq-related storylines, the survey found.

Attention to the war dropped in all five media sectors surveyed. Network evening news, the sector that gave the war the greatest share of attention in the first quarter, scaled back more than 40 percent, from 33 percent in the first quarter to 19 percent in the second, the study showed.

On cable television, another leader in first-quarter coverage, the slide was nearly as great, from 23 percent of news reported to 14 percent -- a drop of 39 percent, the project said.

The bulk of the fall took place after May 24, when Congress approved war funding without including troop withdrawal timetables. This was widely viewed by the media as a victory for President George W. Bush in a political battle with Congress sparked by his January 10 troop "surge" announcement.

"In the aftermath, the debate itself quieted, as did coverage," the report said.

News from inside Iraq in the media surveyed became even more focused on Americans rather than Iraqis in the second quarter, the study found.

Fully 55 percent of coverage about events on the ground dealt with U.S. combat and casualties, U.S. troop activities and soldiers charged with crimes, it said.