A hearing (”taking down sworn testimony”) can be done with only a single senator if such a hearing has been scheduled according to rules. This actually happens more often than might be thought because transcripts are available.
At least two minority party members are required to pass such a nomination to the floor.
https://www.judiciary.senate.gov/about/rules
...1. Seven Members of the Committee, actually present, shall constitute a quorum for the purpose of discussing business. Nine Members of the Committee, including at least two Members of the minority, shall constitute a quorum for the purpose of transacting business. No bill, matter, or nomination shall be ordered reported from the Committee, however, unless a majority of the Committee is actually present at the time such action is taken and a majority of those present support the action taken.
2. For the purpose of taking down sworn testimony, a quorum of the Committee and each Subcommittee thereof, now or hereafter appointed, shall consist of one Senator...
So can the Dems delay this procedure indefinitely just by not showing up? How would judges ever get confirmed?