We have case studies where the Universal Church got it materially wrong down the road.

Let's face it:  The major pushers of this exaggerated UA theory are the sedes, who in their rabid quest to destroy anyone who sees the world differently, view UA in an extreme way, and use it as a "gotcha" test.  They want to trap Trads into a false dichotomy where you either reject a V2 pope right off the bat, or you have to accept him for a lifetime...no ifs, ands, or buts (as is usual with their over-simplistic thinking).  No theologian worth his salt would define UA in such a rigid manner.  

Let's face it:  The major pushers of this exaggerated UA theory are the sedes, who in their rabid quest to destroy anyone who sees the world differently, view UA in an extreme way, and use it as a "gotcha" test.  They want to trap Trads into a false dichotomy where you either reject a V2 pope right off the bat, or you have to accept him for a lifetime...no ifs, ands, or buts (as is usual with their over-simplistic thinking).  No theologian worth his salt would define UA in such a rigid manner.  

I can't believe how stupid you are.  No sede is pushing universal acceptance of Conciliar popes.  Who are the people pushing it here on CathInfo?  It's XavierSem, Praeter, Salsa and Disco.  All SSPX people.  Get your head out of your ass!

1.  I don't think that UA is determined by the laity, or priests, since they have no business in electing him.
2.  It would be determined by the Cardinals, and if they accept him, then it's a sign he's the pope, since it's their job to elect him to begin with.
3.  The fact that many theologians, including +Bellarmine, say that the Cardinals would declare a pope a heretic, gives some credence to the fact that they have the highest priority in all of this.
4.  Regarding +Francis, we already know that 4-5 Cardinals signed the "dubia" letter, as a sign that there is not UA concerning his orthodoxy.  I do not know if there are any Cardinals who think that +Benedict's resignation is null.
5.  I don't think any Trads have to worry about proving any V2 popes were not elected (except for sedes).  I'm perfectly fine with the theory that they were validly elected, but immediately spiritually impaired due to heresy (either before or after the election, and most likely, both).
6.  UA is not really important, for our present situation.  What matters more is the litmus test of orthodoxy, which all V2 popes fail in miserably.

Let's face it:  The major pushers of this exaggerated UA theory are the sedes, who in their rabid quest to destroy anyone who sees the world differently, view UA in an extreme way, and use it as a "gotcha" test.  They want to trap Trads into a false dichotomy where you either reject a V2 pope right off the bat, or you have to accept him for a lifetime...no ifs, ands, or buts (as is usual with their over-simplistic thinking).  No theologian worth his salt would define UA in such a rigid manner.  

UA, if true, would DISPROVE sedevacantism entirely. You're literally accusing sedes of pushing a theory that would disprove their position. Just blindly accusing your pet boogeyman of believing everything you disagree with. 

Let's face it:  The major pushers of this exaggerated UA theory are the sedes, who in their rabid quest to destroy anyone who sees the world differently, view UA in an extreme way, and use it as a "gotcha" test.  They want to trap Trads into a false dichotomy where you either reject a V2 pope right off the bat, or you have to accept him for a lifetime...no ifs, ands, or buts (as is usual with their over-simplistic thinking).  No theologian worth his salt would define UA in such a rigid manner.  

I see this as the opposite.  UA is being pushed by R&R in an attempt to demonstrate that these men are legitimate popes.

UA is tangential to sedevacantism.  Whether or not and to what extent Catholics must obey a legitimate pope is the point of dispute between sedevacantists/privationists and R&R.

This is what I was always taught...

Catholic Encyclopedia, 1911
Seems simple enough to me.    

I know we disagree on the sedevacantist issue , but I'm glad you're back and welcome!

The whole idea of Universal Peaceful Acceptance is that the identity of the pope is a dogmatic fact if he receives it. Well, maybe Francis *arguably* hasn't, but every other V2 pope certainly has. So if UPA is true then all those V2 popes were valid popes, utterly destroying the sedevacantist position.

You're begging the question.  You're falsely assuming that the other V2 papal claimants had UPA.  I disagree with that.

The whole idea of Universal Peaceful Acceptance is that the identity of the pope is a dogmatic fact if he receives it. Well, maybe Francis *arguably* hasn't, but every other V2 pope certainly has. So if UPA is true then all those V2 popes were valid popes, utterly destroying the sedevacantist position.

Yup. Also if the Papacy of His Holiness Pope Ven. Pius XII is not a priori known to be an infallibly certain dogmatic fact, neither could we know with absolute certainty, as we must, that the dogma of the Assumption defined by His Holiness is certainly true. In other words, if we could doubt his legitimacy, we could doubt the dogma. But it is heretical to say we can doubt a dogma. Hence, it must necessarily be true that the Papacy of a Universally Accepted Pope - such as all admit Pope Pius XII to be - is a dogmatic fact.

Further, it is proved by the indefectibility of the Ordinary and Universal Magisterium of the Church. For this reason, Pope Pius XII himself, in the dogmatic Bull declaring the dogma of the Assumption, says that the universal consensus of the Bishops, was already an infallible sign that the doctrine was true and definable. The principle of universal acceptance is same. Canonists and theologians say "universal acceptance is not the cause (the Pope being elected and accepting is the cause) but is a sign and infallible effect of a valid election". That is, if universal acceptance was present, it could only have been the effect of a certainly valid election being concluded.

One Caveat: I don't think any author, as far as I know, including St. Alphonsus, was speaking of the "second-man" scenario. As discussed. Thus, when St. Alphonsus says, "It is of no importance that in the past centuries some Pontiff was illegitimately elected or took possession of the Pontificate by fraud; it is enough that he was accepted afterward by the whole Church as Pope, since by such acceptance he would become the true Pontiff." this does not apply, I believe, when there is a sitting Pope already reigning whom someone else is opposing or trying to unseat. That's AFAIK, and it may be wrong, but that's what I think. But as far as appears, it does apply in every other case, for the reasons already mentioned.