I recall MarkLevin was calling for Rs to do this over GWB's judges being blocked in ~ 2006 but the gang of 14 made a deal with each other to stop the rules change, which was just as well as Rs lost the Senate the next year..
According to the Supreme Court ruling in United States v. Ballin (1892), changes to Senate rules could be achieved by a simple majority, but only on the 1st day of the session in January or March. Nevertheless, under current Senate rules, a rule change itself could be filibustered, with two-thirds of those senators present and voting (as opposed to the normal three-fifths of those sworn) needing to vote to break the filibuster.[44] Despite this written requirement, the possibility exists that the filibuster could be changed by majority vote, but only on the 1st day of the session in January or March, using the so-called nuclear option, also sometimes called the constitutional option by proponents. Even if a filibuster attempt is unsuccessful, the process takes floor time
Wika: Filibuster
Rules can be changed by a simple majority on the first day of the session. For 224 years, however, the Senate has operated with the understanding that, unlike the House whose members are chosen anew every two years, it is a permanent body since only 1/3rd of its members are renewed at each election. Thus whereas the House drafts its rules anew after each election, the Senate continues to operated on its standing rules which require 2/3 vote to change.
What Harry Reid is proposing is ignoring this precedent and act as if the incoming Senate is a new body which can then adopt its rules be a simple majority vote.