To know who's on your side (and who's not), all you need to do is follow the money. D.C.-based ultra-conservative groups are spending millions of dollars this election cycle in anonymous "dark money" to promote their favored candidates. But these funds come with strings attached. Candidates with the backing of these powerful organizations are committed to their full agenda — which includes promoting right-to-work-for-less, weakened workplace protections and an end to Wall Street regulation.

Here are some of 2014's top candidates, and the groups behind them.

Content Sources: Campaign finance disclosure and political spending listed on www.opensecrets.org; numerous official Associated Builders and Contractors websites from across the U.S.

Photos courtesy of U.S. Senate and candidate websites or sourced under a Creative Commons License from Wikimedia.org and Flickr.com