Chamber drops $10 million on ads in 20 races

The Chamber will target 12 House races and eight Senate contests.

Some of the spots are negative ads targeting Democrats including Rep. Tammy Baldwin (Wis.), Sen. Claire McCaskill (Mo.), Sen. Jon Tester (Mont.) and former Gov. Tim Kaine (Va.), who is running for Senate in Virginia.

Others will be positive spots lauding candidates for their achievements in creating jobs, promoting tourism and backing free-enterprise principles. Those ads will promote candidates including Sen. Dick Lugar (R-Ind.), Rep. Rick Berg (R-N.D.), Rep. Dan Lungren (R-Calif.), Rep. Fred Upton (R-Mich.) and former Gov. Linda Lingle (R-Hawaii), who is running for Senate.

The Democratic Senatorial Campaign Committee fired back at the Chamber's ad buy.

“Every one of the Republican Senate candidates that is benefiting from these ads sides with private insurance companies over seniors, with big oil companies over small businesses, and with billionaires over middle class families. Voters are going to see these attacks for what they are and all the money in the world won’t be able to distract from the Republican special interest in agenda," said DSCC spokesman Matt Canter.

— This post was updated at 10:49 a.m.