This story was originally published by The Center for Public Integrity, which is a nonprofit, nonpartisan investigative news organization in Washington, D.C.
American Crossroads, the conservative super PAC behemoth that slumbered through 2013, is awakening.
In recent days, the group has spent more than $187,000 on negative advertisements targeting Democrats, according to a Center for Public Integrity review of filings with the Federal Election Commission.
Of that sum, about $137,000 went toward television ads critical of John Walsh, the Montana Democrat who will be sworn into office Tuesday to replace Max Baucus, the veteran legislator who the Senate last week confirmed as the next U.S. ambassador to China.
Another $50,000 funded mailings opposing Alex Sink, the Democrat running in the March 11 special election in Florida's 13th Congressional District. Politico has reported that TV ads are also in the works. The seat has been vacant since the death in October of Republican Rep. Bill Young.
American Crossroads, co-founded in 2010 by GOP strategists Karl Rove and Ed Gillespie, has vowed to help the GOP wrest control of the U.S. Senate away from Democrats in November and expand the Republican majority in the U.S. House of Representatives.
To gain a Senate majority this fall, Republicans need to pick up six new seats, and the contest in Montana could be one of the determining races.
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Ahead of the 2010 and 2012 elections, American Crossroads used its vast financial resources to boost its favored candidates and attack against Democrats.
It was the top-spending super PAC during the 2010 midterm elections, at roughly $22 million. And during the 2012 election cycle, it spent about $105 million -- more than every other super PAC, with the exception of pro-Mitt Romney group Restore Our Future.
Crossroads GPS -- a controversial nonprofit group affiliated with American Crossroads -- has also been a major attack dog against Democrats.
In 2013, American Crossroads did not directly fund any political advertisements, although it did transfer $53,000 to another super PAC that backed Republican Gabriel Gomez during a special U.S. Senate election in Massachusetts.
Heading into 2014, American Crossroads reported about $2.7 million in the bank. Its largest donor last year included Contran Corp., the company of Texas billionaire Harold Simmons who died in December, which gave $1 million. Coal industry executive Joe Craft gave $500,000 through a trust.