Traditionally, political parties and their campaign arms spend the most amount of money promoting their congressional and senatorial candidates across the country. Following the Supreme Court’s decision in Citizens United, however, a flurry of outside groups has materialized with gigantic war chests. As profiled in After Citizens United: A Look into the Pro-Corporate Players in American Politics, the Court’s decision allowed for new groups to surface and older organizations to increase their fundraising capacities. In the midterm elections, Kristin Jensen and Jonathan D. Salant of Bloomberg report that political committees supporting Republicans and attacking Democratic officials have so-far outspent both the Republican and Democratic parties’ campaign arms in 2010:

Republican-leaning groups outspent the two political parties combined during September’s first four weeks in a bid to sway the U.S. congressional elections, Federal Election Commission reports show.

The groups — including Crossroads GPS, advised by Republican strategist Karl Rove, and the U.S. Chamber of Commerce — spent more than $33 million, mainly on advertising. That compares with just under $20 million spent by the Republican and Democratic committees charged with electing their party’s candidates.

Outside organizations are focusing most of their fire on Senate races, particularly in California, Colorado, Florida, Missouri, Nevada and Pennsylvania, their reports to the FEC show. Many of the groups are registered as nonprofits that don’t have to disclose their donors, drawing protest from Democrats including President Barack Obama and Montana Senator Max Baucus.

“Republican operatives in the shadows are clearly winning the hidden money game,” said Linda Fowler, a government professor at Dartmouth College in Hanover, New Hampshire.

Obama has used two of his recent weekly addresses to blast Republicans for blocking legislation that would make groups engaged in political activity report their contributions. Baucus, the Senate Finance Committee chairman, today asked Internal Revenue Service Commissioner Doug Shulman to investigate the organizations.

While political parties and their campaign arms must disclose their donors and have caps on contribution amounts, many outside groups accept unlimited amounts of money from individuals and corporations and do not have to disclose the sources of their funding. Thanks to such organizational advantages, such outside groups are now overshadowing political parties as regulations concerning transparency and spending fall by the wayside.