That’s a good example, UDS. There are some extremely conservative Roman Catholics who believe that Cardinal Siri was elected in the papal conclave in 1958 to succeed Pius XII, but was forced to renounce, and then the conclave elected John XXIII, so that all subsequent appointments to the cardinalate were invalid, which in turn means that all subsequent papal elections were invalid. The legitimacy of Vatican II is also undermined by this thesis, since John lacked the papal authority to summon a council.
See: Siri Thesis.