“Expected” is important because their votes aren’t disqualified if they don’t adhere to expectations or anything

Oh boy. Yeah, the clash between convention and rule is something I'm familiar with. In Australia, like America, our federal Senate technically represents the state, not the people (which is the job of the House of Representatives). As such, historically, a vacancy caused by death or resignation was filled by someone chosen by that state's legislature. By convention, they would choose the person nominated by the previous Senator's party. Crucially, in 1975 my state's legislature was run by what was effectively an authoritarian dictatorship using gerrymandering and other political tricks, as well as police brutality to hold on to power for 19 years. In '75 it was 7 years into that reign, while the federal government had the most left-wing leadership in the country's history. When one of their federal Senators died at a time when the Senate was already on a knife-edge, my state's legislature took the opportunity to break from convention and nominate someone who would not support the incumbent federal government.

This in turn provided the opportunity to break another convention. This one's a little more difficult to explain, but it has reverberated so strongly in Australian political history that it is known as simply "The Dismissal", or the less catchy "1975 Australian Constitutional Crisis." In summary: when the Senate failed to pass the government's budget (something made possible in part thanks to the unconventionally-appointed Senator), the normal thing to do would be for the Prime Minister to go to the Governor General (the monarch's official representative) and request a new election, or a special kind of election called a "double dissolution" election. Australia normally elects only half its Senate in an election, but with a double-dissolution it re-elects the whole Senate. By convention the Governor General is entirely a figurehead, and just goes ahead with what the Prime Minister requests. In this case, instead of doing that, he fired the PM and appointed the minority leader as the new PM, at which point the previously-opposition Senators turned around and passed the exact same budget they were previously opposing. Incidentally, there are strong reasons to believe that the GG's actions here were in part influenced by CIA involvement, including the fact that in the lead-up to it the US sent someone nicknamed "the coupmaster" as their Ambassador, and the fact that the government had been threatening to close down the important CIA base at Pine Gap.

These were in Australia, where because we use the Westminster system there's a tradition of conventions being much, much stronger than they tend to be in America.

Anyway, thanks for sharing the details of the American process. I appreciate it.