House Majority PAC has canceled airtime aimed at House races in the pricey Miami, Boston and St. Louis markets.

In the past 24 hours, the Democratic super PAC pulled a $510,000 week-long buy in Miami for Oct. 9, $439,000 in St. Louis during the same week, and has canceled $637,500 for a two-week buy in the Boston market, according to sources in both parties who tracks ad buys.

The Miami market covers embattled Rep. David Rivera’s (R) district, which the super PAC planned to target. The St. Louis market covers two competitive open-seat races in Illinois: the the 12th and 13th districts. There are three Members in competitive races covered by the Boston media market: Reps. John Tierney (D-Mass.), Frank Guinta (R-N.H.) and Charles Bass (R-N.H.).

a form of political triage

House Majority PAC spokesman Andy Stone pointed to a Miami Herald report out today as proof that the Democratic nominee will prevail over Rivera in Florida. The newspaper reported that a failed Democratic primary candidate told the FBI that Rivera was behind his candidacy. The DCCC has reserved $1.5 million airtime in Miami in the final weeks before Election Day, but the National Republican Congressional Committee has not put a hold on any time for Rivera’s race.

In southern Illinois, it’s unclear how much TV time the party committees will end up buying for the pair of House races. Both party committees have spent money on these races and hold future reservations in the St. Louis market. But either party could pull its reservations in the final weeks if it appears that the race is beyond salvaging.

“Nothing about the move should reflect at all our confidence that John Tierney will win the race,” Stone said. “Both Democrats in 12th and 13th [districts in Illinois] are in incredibly strong positions and running great races against out-of-touch, Tea Party Republicans.”