The legislation would require the identity of donors who give at least $10,000 to be disclosed but is likely to fail on Wednesday.
Curtailing the right to associate and speak anonymously would do profound damage in the current political climate.
The payments indicate an ongoing financial relationship between the rally's organizers and Trump's political campaign.
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