The DCCC is reserving air time in 40 House districts so far, according to the New York Times:

The Democratic Congressional Campaign Committee reserved television time in 40 districts across the country, including those of Representatives John M. Spratt Jr. of South Carolina, chairman of the Budget Committee, and Ike Skelton of Missouri, chairman of the Armed Services Committee. The committee also reserved time to help Representative Chet Edwards of Texas, who is seeking his 11th term in November and is among the party’s most vulnerable members.