> The Constitution clearly contemplates these situations where the vice president's vote wouldn't matter, so it stands to reason that the Senate is free to adop

> The Constitution clearly contemplates these situations where the vice president's vote wouldn't matter, so it stands to reason that the Senate is free to adopt rules requiring a different vote threshold than simple majority. Just a note that the Supreme Court has generally reached the opposite conclusion to this in situations where the Constitution specifies special behavior. The general philosophy seems to be: if the Constitution specifies conditions under which there is a special behavior, that special behavior can _only_ apply under those conditions. For example in Reynolds v. Sims [1], the Court held that state legislature districts had to have roughly equal population sizes even though the US Senate by design has districts of dramatically different populations sizes. The existence of a specific exemption to "one person one vote" in the US Constitution doesn't permit other exemptions. I feel there's a similar thing with presidential qualification. The Constitution lists certain conditions (e.g. 35 years or older), but then Congress can't add additional conditions. [1] https://en.wikipedia.org/wiki/Reynolds_v._Sims https://en.wikipedia.org/wiki/Reynolds_v._Sims