What's at Stake: Democracy: How Captured Courts Support the Republican Party's Assault on American Democracy [open pdf - 5MB]
From the Document: " Recent Republican-appointed justices' Supreme Court rulings have opened the door for unlimited political spending by special interests, making it harder for the voices of Americans to be heard.  These decisions have undercut free and fair elections and led to voter suppression.  Outside conservative groups, many of which are not required to disclose their donors, have spent millions of dollars to advance their policy agendas before the courts. A number of these same groups are now working to undermine access to the ballot in the 2020 election.  President Trump's judicial nominees, as well as judges nominated by previous Republican presidents, are responsible for the vast majority of decisions that have resulted in voter suppression and made it nearly impossible to regulate political spending."
U.S. Senate Democrats: https://www.democrats.senate.gov/