One of the very few enumerated power in the Constitution is that the Senate and House get to make their rules however they see fit. What usually happens is that

One of the very few enumerated power in the Constitution is that the Senate and House get to make their rules however they see fit. What usually happens is that at the beginning of the new Congress the first order of business for each body is to set the current rules. Part of those rules are how to change the rules during the current. It's common for these to be passed unanimously.