Except that after Vatican I, there is no mechanism for the clergy to declare a Pope in error. It used to be the Cardinals or the University of Paris had some say, but that is gone now.
So if the Pope declares that divorce and remarriage is no ok, Catholic's pretty much have to pretend it was always ok.
That would be to deny Christ, which is not within the purview of any man, including the pope.
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"Therefore now they are not two, but one flesh. What therefore God hath joined together, let no man put asunder. [7] They say to him: Why then did Moses command to give a bill of divorce, and to put away? [8] He saith to them: Because Moses by reason of the hardness of your heart permitted you to put away your wives: but from the beginning it was not so. [9] And I say to you, that whosoever shall put away his wife, except it be for fornication, and shall marry another, committeth adultery: and he that shall marry her that is put away, committeth adultery. [10] His disciples say unto him: If the case of a man with his wife be so, it is not expedient to marry.
[9] Except it be: In the case of fornication, that is, of adultery, the wife may be put away: but even then the husband cannot marry another as long as the wife is living."
http://www.drbo.org/chapter/47019.htm
85 "The task of giving an authentic interpretation of the Word of God, whether in its written form or in the form of Tradition, has been entrusted to the living teaching office of the Church alone. Its authority in this matter is exercised in the name of Jesus Christ."47 This means that the task of interpretation has been entrusted to the bishops in communion with the successor of Peter, the Bishop of Rome.
86 "Yet this Magisterium is not superior to the Word of God, but is its servant. It teaches only what has been handed on to it. At the divine command and with the help of the Holy Spirit, it listens to this devotedly, guards it with dedication and expounds it faithfully. All that it proposes for belief as being divinely revealed is drawn from this single deposit of faith."48
http://www.vatican.va/archive/ccc_css/archive/catechism/p1s1c2a2.htm