Public Citizen's analysis found that casino magnate Sheldon Adelson and his wife were the largest individual super PAC contributors since Citizens United.
Earlier this month, Tempe residents voted 9-1 to require "dark money" groups to disclose their donors. The Arizona Legislature then moved almost immediately to effectively nullify the vote.
Congress used a must-pass spending bill to shield anonymous political money, but government watchdogs said it could have been much worse.
From Maine to Montana, even conservatives are rethinking the flow of dark money into politics.
When they're over, the 2014 midterm elections will have cost nearly $4 billion
This year, the greatest amount of dark money, more than $50 million, has been spent on boosting Republicans and defeating Democrats.
Since the IRS got burned over nonprofits, anonymous donors know they can spend, spend, spend