History. 3 of 5: parliament chose from the party's official list in 1965, 1995 and 2002; it chose another party member in 1993 (first vote) and 2000.
Hunch. The Swiss People's Party rules, in the version in force since April 2022, say a member who accepts the seat without the party's nomination loses membership at once.
The party list market resolves on the same parliament page and on the list the Swiss People's Party group adopts on 20 November: YES if the first person declared elected on 9 December is on that list, and NO if it is anyone else. With no list or no one elected that day the market is VOID, and RFI and swissinfo are the backups.
We looked for cases where a minister from the Social Democrats on the left or the Swiss People's Party on the right left the government in the middle of a term, and parliament filled only that one seat that day. We found five such elections since the seats were first shared out in 1959. Each time the party of the minister who left kept the seat. (Swiss Parliament; Swiss Parliament; swissinfo; RFI)