Since January 2010, spending by outside organizations to influence congressional elections totals some $57 million--up more than $20 million from a comparable time period in 2006, the most recent non-presidential election cycle--according to reports collected by the Federal Election Commission. 

Though the rising independent expenditures--money spent by outside groups on anything from phone banks and mailing lists to negative political ads to influence a federal election--come after the Supreme Court decisions that weakened campaign finance laws, it's unclear whether those rulings are fueling the boom.

While some labor unions have taken advantage of the rulings to directly make independent ...