The lack of support among a handful of Senate Democratic incumbents is a major blow to the effort to change the upper chamber’s rules.

Democratic leaders in both the House and Senate are pushing for filibuster reform at the start of the new Congress next year.

Five Senate Democrats have said they will not support a lowering of the 60-vote bar necessary to pass legislation.

Another four lawmakers say they are wary about such a change and would be hesitant to support it.