Did sedevacantism exist prior to Vatican 2?

My early research hasn't detected anything in Church history on the same level as the sedevacantism that originated with Vatican 2.

There have been around 40 antipopes but always when there was another sitting pope. The current period is unprecedented

The current period is unprecedented because it is The Great Apostasy of the End Times but there hasn't always been another sitting pope.  There have been various periods where there has been no pope.

Did sedevacantism exist prior to Vatican 2?

My early research hasn't detected anything in Church history on the same level as the sedevacantism that originated with Vatican 2.

My early research has detected that an apostacy such as Vatican II has never affected the Church before. 

Yes. Sedevacantism is taught by all the Fathers of the Church, as St. Robert Bellarmine tells us. Fr. Cekada's pamphlet here cites numerous pre-Vatican 2 theologians in favor of sedevacantism.

Actually, it is recognize and resist that does not exist before Vatican 2.

Pope Paul IV taught R&R in 1559 in his Apostolic Constitution, cuм ex Apostolatus Officio...

1.In assessing Our duty and the situation now prevailing, We have been weighed upon by the thought
that a matter of this kind [i.e. error in respect of the Faith] is so grave and so dangerous that the Roman
Pontiff,who is the representative upon earth of God and our God and Lord Jesus Christ, who holds the
fulness of power over peoples and kingdoms, who may judge all and be judged by none in this world,
may nonetheless be contradicted if he be found to have deviated from the Faith.

This shows that he taught that not only is a heretical pope possible, he also told us what to do about it.

My early research hasn't detected anything in Church history on the same level as the sedevacantism that originated with Vatican 2.

.

This is a bit of an odd claim. Can you tell us a little about your research? Did you read Canon 188 of the 1917 code of canon law, for example?

This is a bit of an odd claim. Can you tell us a little about your research? Did you read Canon 188 of the 1917 code of canon law, for example?

Yeti, no.  I had not read the Code of Canon Law before your suggestion above.  A quick look at it reminds me of legal docuмents, which means not intended for a general audience.

Is the section below what you referenced?  If so, I have some questions:

• What does "by tacit resignation recognized by the law itself" mean?
• Is the Pope considered a "cleric"?
• I don't believe any Pope in recent history has publicly defected from the Catholic faith.  What does "publicly defect" mean?  I guess I expect some event similar to Benedict 16th's public resignation.
• This one seems simple, but it gets more complicated the longer I think about it.
  How would you define "the Catholic faith"?

Canon 188


Any office becomes vacant upon the fact and without any declaration by tacit resignation recognized by the law itself if a cleric:
...
4. Publicly defects from the Catholic faith;
...