Sen. Sherrod Brown (D-Ohio) will receive some help from the League of Conservation Voters in his reelection campaign over the next two weeks.

The group has purchased a six-figure TV ad buy in Columbus, asking Ohioans to "call Sen. Brown; thank him for fighting to bring manufacturing jobs home to Ohio."

The ad arrives two weeks after Brown voted to extend expiring tax credits to companies that invest in renewable energy. The group says these credits contribute to Ohio's growing clean energy industry.

Brown is facing a closely watched reelection campaign against the state's Republican Treasurer Josh Mandel, and conservatives are targeting the race as a top priority.

In December, The Huffington Post reported that the race had attracted more third-party spending from Republican groups than any other.

More than one year before any vote would be cast, conservative groups like the U.S. Chamber of Commerce and Crossroads GPS had dumped nearly $2.9 million into the Ohio race in support of the GOP candidate.

More recently, political action committee the Club for Growth received a $500,000 check from Sen. Jim DeMint (R-S.C.) for the expressed purpose of helping Mandel and three other candidates endorsed by DeMint.

The Sunlight Foundation reported Wednesday that DeMint's decision to favor Club For Growth over a more traditional donation to the National Republican Senatorial Committee shows a trend suggesting that super PACs and third-party groups are quickly eroding the more traditional ways that campaigns are financed.

Watch the LCV ad: