Chamber expands Senate ad blitz to five more states

This is the latest volley from the group. It spent a combined $1.4 million on Senate races in Hawaii, Nevada, New Mexico and North Dakota earlier this month.

The ads hit Democratic Sens. Bill Nelson (Fla.), Jon Tester (Mont.), and Sherrod Brown (Ohio) as well as Rep. Tammy Baldwin (D-Wis.) for backing the Democratic health insurance reform law, and slam Rep. Martin Heinrich (D-N.M.) for opposing expanded drilling for oil and immediately building the Keystone XL pipeline.

The group does not disclose how much it spends on ads and did not respond to a request for comment on this ad buy.

The Democratic Senatorial Campaign Committee fired back, accusing the Chamber of spending "secret money" to prop up "weal candidates."

"These Republican candidates would be nothing more than a rubber stamp for the Chamber’s special interest agenda that puts insurance companies over seniors, oil companies over small businesses, and billionaires over the middle class," said DSCC spokesman Matt Caner. "As voters learn more about the Republicans' special interest agenda, they'll quickly realize how wrong these priorities are for their families and our country."

Watch the ad against Heinrich:

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