The U.S. Chamber of Commerce, a conservative group representing businesses and trade organizations, is launching ads in four hotly contested Senate races, the organization announced today.

"We need leaders in the Senate who understand that free enterprise and not more government will lead the American recovery," said Thomas Donohue, the president and CEO of the Chamber in a statement. "Our efforts underscore the importance of electing a pro-business Senate that will be focused on good long-term transportation policy, increased energy production, and fiscal responsibility to bring our economy back."

The Chamber of Commerce traditionally supports Republican candidates- although they have on occasion endorsed Democrats who they believe to be business friendly. Their ads launched in the battleground Senate states of Hawaii, Nevada, North Dakota and New Mexico each support the state's respective Republican nominee.

The ads, which can be viewed here, are specific to each state's race, but in general they highlight the issues that the Chamber advocates for; free enterprise, less government spending and the repeal of the Affordable Care Act.

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The Democratic Senatorial Campaign Committee wasted no time in responding to the Chamber's latest round of ads.

"The US Chamber of Commerce knows Republicans like Linda Lingle, Dean Heller, Heather Wilson, and Rick Berg will put corporate special interests ahead of middle class families in Washington. That's exactly why the Chamber is spending millions in secret money to prop up these weak candidates," spokesman Matt Canter said in a statement referring to the Republican candidates in Hawaii, Nevada, New Mexico and North Dakota.

The group has not provided a specific figure for how much they plan to spend this election cycle, but at a breakfast with reporters back in May, Donohue suggested that the group would be spending at least $50 million. The group has so far invested in House and Senate races.

The Chamber of Commerce is another example of the so-called "shadow groups" which have become increasingly present in this election cycle. Because the chamber is classified as a trade organization they are not required to disclose their donors, so it is not possible to know who has donated.