A conservative advocacy group today kicks off a huge ad campaign in 11 states and two dozen of the most competitive congressional races, slamming "wasteful federal spending."

The $4.1-million ad buy from the Americans for Prosperity Foundation does not mention individual candidates in the November elections. The script attacks Washington policies, describing the economic stimulus program as a failure and declaring that "wasteful spending must stop."

The ads — part of a midterm election likely to be the most expensive on record — will run in 27 media markets through August. Democrats hold all but one of the 24 House seats, including 17 incumbents seeking re-election.

The TV buys are in Arkansas, Indiana, Michigan, Missouri, North Dakota, Ohio, Pennsylvania, South Carolina, Tennessee, Virginia, and Wisconsin. Several of those, including Ohio, Pennsylvania and Missouri, also have tight Senate races.

The group is expected to continue funding ad buys throughout the fall and across the country.

Its donors are a mystery but are presumed to include David Koch, founding chairman of the AFP foundation and a prominent conservative donor.

"This is the biggest ad buy I am aware of this summer," said Rep. Chris Van Hollen of Maryland, chairman of the Democratic Congressional Campaign Committee. "We say, 'Viewer beware.' These are sponsored by people who support the Bush economic agenda. ... They are running these ads on behalf of GOP candidates who want to return to the Bush agenda and support efforts to export American jobs."

He and other Democrats specifically mentioned Koch, whom they accuse of shipping jobs overseas via his privately held energy company, Koch Industries.