In 1964, as Southern Democratic Senators staged a filibuster, which ran 54 days to block passage of the Civil Rights Act of 1964, Dirksen, Thomas Kuchel (R-CA), Hubert Humphrey (D-MN), and Mike Mansfield (D-MT) introduced a substitute bill that they hoped would attract enough swing votes to end the filibuster. It was weaker than the House version, on the government's power to regulate the conduct of private Business, but it was not so weak it would cause the House to reconsider the legislation. Also, the Department of Justice said the Mansfield-Dirksen Amendment would not prevent effective enforcement. However, Senator Richard Russell, Jr. (D-GA) refused to allow a vote on the amendment. Finally, Senator Thruston Morton (R-KY) proposed an amendment that guaranteed jury trials in all Criminal contempt cases except voting rights. It was approved on June 9, and Humphrey made a deal with three Republicans to substitute it for the Mansfield-Dirksen Amendment in exchange for their supporting cloture on the filibuster. Thus, after 57 days of filibuster, the substitute bill passed in the Senate, and the House–Senate conference committee agreed to adopt the Senate version of the bill.