AKA, everything you may have wanted to know about Senate voting rules but didn’t really care enough about to ask
The short answer is no – the size of the majority required on any given vote in the Senate is codified in the Constitution in many cases, and in the rules of the Senate in others.
Insofar as I can tell, very few things require an actual two-thirds majority. That list includes (but is not limited to):
- Votes to invoke cloture on a motion to amend Senate rules (although there seem to be some ways around this one, as evidenced by first the Democrats and then the Republicans jettisoning the filibuster for certain types of presidential nominees)
- The decision to ratify a treaty (or to postpone ratification indefinitely)
- A vote to sustain articles of impeachment
- Passing a bill by overcoming a presidential veto
Much more frequently, the Senate is asked to meet a three-fifths threshold ( 60 votes) to invoke cloture (aka, to end debate) on a given subject (which needs to happen before something can actually be voted on). Prior to a cloture vote, Senators are allowed to speak for as long as they so choose… hence the filibuster, which, in the glory days of the filibuster, basically meant speaking and speaking and speaking so nobody could call for a vote. These days, since it is so rare that 60 Senators agree on anything, you can “filibuster” simply by denying the majority party the 60 votes to end debate. Once cloture is invoked, there are very specific rules on how long each Senator can speak, when and how amendments can be added, how long discussion can last before a vote is required, etc.
While these rules are pretty well established at this point, it is worth noting that they are NOT derived directly from the Constitution (which, other than in a handful of instances, dictates that the Senate can set its own rules). Instead, they are the result of Senate rules passed into being at later times by (you guessed it!) a two-thirds majority of the members present.
For example, in the early days of Congressional politics, it was an enshrined principle that Senators were entitled to unlimited debate on any topic they so chose, which meant that it was almost impossible to bring a vote on any measure that generated lots and lots and lots of debate. It wasn’t until 1917 that the Senate adopted Rule XXII (yes, they do count all XLIV rules in Roman numerals), which allows for the now-notorious three-fifths-majority cloture vote. Similarly, the reconciliation process (which is how the ACA was passed into being, and how McConnell attempted to pass his repeal bill[s]) did not exist until the Congressional Budget Act of 1974 established the idea that one per budget, you can open limited debate on and pass a bill that redirects funds without increasing their spending. This process has all sorts of limitations (see the next explanation?), but because you only need 51 votes to invoke cloture, it is a way around the 60 vote threshold.
So back to the original question – can you somehow force the Senate to increase its voting threshold to a two-thirds majority? – the short answer is still no, and the longer answer remains no, unless two-thirds majority of Senators votes to change the rules of the Senate. History implies that this is very unlikely, as most historical changes made have lowered the threshold, rather than increased it. And here’s the thing – what looks like a terrible overreach of power when your party is in the minority (see: McConnell’s ACA repeal attempts) looks like a reasonable way around an obstructionist bloc of naysayers when your party is in the majority (see: the passage of the ACA, circa 2010). So that strikes me as rather unlikely.
The (current) Rules of the Senate: https://www.rules.senate.gov/public/index.cfm?p=RulesOfSenateHome
More specifically, Rule XXII:
The delightfully searchable version of the Senate Manual for the 113th Senate, which is the last time the complete Senate Manual was published in PDF form:
“Filibuster and Cloture”:
Congressional Budget Act of 1974:
Article I of the Constitution: