( CNN ) -- What do they have to be ashamed of ? Several years ago , I caught one of my kids sneaking out of the house . Like any mom , I was more than a little mad and demanded an explanation . `` But Mom , I was n't doing anything wrong -- I was just hanging out with my friends , '' was the response I got , but I knew better . The truth is that if you do n't have anything to be ashamed of , you have no reason to be sneaking around . This election season , special interests are sneaking around trying to influence voters by funding the attack ads you see on TV . With the help of a recent court ruling , they can do it all anonymously . It 's hard not to think it 's because they have something to be ashamed of . In January , the Supreme Court gave corporations , unions and special interest groups the power to influence elections in an unlimited and anonymous way . In an unprecedented move , the court , the same majority who decried an activist court when they were nominees , legislated from the bench and overturned years of previous case law , striking down longstanding limitations on campaign spending from special interests in the case of Citizens United v. Federal Election Commission . Before Citizens United , corporations and unions could not spend money to run ads expressly advocating one candidate over another . Now they can . But what is worse , they can anonymously donate millions of dollars to `` nonprofit '' groups , which buy the ads without having to disclose who truly paid for them . The ruling essentially opened the barn door to anonymous , unlimited corporate donations to sway voters . Americans have a lot to be frustrated about right now with our economy , and I know many are anxiously awaiting their opportunity to weigh in on the country 's future by voting on November 2 . The idea that special interests are trying to secretly buy this election should make their blood boil . Although every member of Congress should be trying to stop this , that is not the case . Republicans have blocked legislation that would help bring these donors to light . A bill offered by Sen. Chuck Schumer , which I co-sponsored , would have forced corporations and unions that want to spend money on campaign ads to be transparent with the public about their political contributions and their donors , while also banning political spending from foreign entities . But each time the bill has received a vote , Republicans have made sure it failed . This bill would n't favor one side or the other : From the most conservative groups to the most liberal , any special interest group spending money on campaign ads would have to be honest about where their funding comes from so voters know whose interest they really represent . Republicans spend a lot of time decrying activist court decisions , yet when it comes to overturning campaign limits and disclosure rules for special interests , they seem to have changed their minds . The reality is that special interests are trying to buy our government this cycle , and Republicans think that 's OK. Well , I do n't . My position is simple : If you are for someone or something , you should be willing to say it out loud . The voters deserve to know . Right now , these shadowy organizations are refusing to produce a list of their donors , and that 's something voters need to consider in November . My rule of thumb is , if I ca n't find out who 's paying for the ad , I do n't believe it . When my teenager tried to pull a fast one on me , I said if you 're not willing to own up to it , how do I know you 're not doing something wrong ? This election cycle , special interests are trying to get away with buying this election without being held accountable . Until they are more forthcoming with where the money is coming from , how can voters believe a word they say ? The opinions expressed in this commentary are solely those of Sen. Claire McCaskill .
Corporations , unions , special interest groups can fund campaign advertising anonymously . Comment: Republicans opposed bill to force disclosure of donors ' names and amounts , she writes . The rule of thumb is , McCaskill says , if you ca n't find out who 's paying for the ad , do n't believe it .