Matea Gold for WaPo:

Senate Majority Leader Harry Reid’s relentless attacks on the billionaire Koch brothers are having an unforeseen impact — spurring other wealthy GOP donors to give more money to groups that keep their supporters’ names secret.

Several prominent pro-Republican advocacy groups say they are benefiting from a burst of cash as some donors — fearful of harsh public attacks such as those aimed at the Kochs — turn away from political committees required under federal law to reveal their contributors.