On the canon, Roman Catholics frequently argue that an infallible decision of the Roman church is needed to secure the exact table of contents of the Bible. The canon was definitively settled for Roman Catholics at Trent. Roman apologists argue that the Holy Spirit worked through Trent to secure an infallible canon.
Now, consider the recent cardinals that picked a new pope. Roman Catholic apologist Jimmy Akin recently wrote:
God Guides the Church: We can be confident of the general principle that God guides his Church. This is something we have biblical assurance of. But his guidance does not prevent human free will from operating, and that means there is the potential for humans to abuse their free will. That applies to the college of cardinals, too, even when they are electing a pope. They do not lose their free will.
I would argue that for the canon, an infallible church is not needed. God can determine His canon using a fallible church in the process.Human Failure in History: We have been very fortunate in recent times to have a series of very holy, wise popes, but this has not always been the case. If you look at history, certain popes have been real scoundrels, like Pope Benedict IX (first elected in 1032). He was elected pope when still a boy. His reign was scandalous. He insisted upon monetary compensation in order to get him to resign. And then he didn't stay resigned. He was the only man to ever hold the papacy more than once. (In fact, he may have held it as many as three times.) Without going into all the scandals attributed to him, the Catholic Encyclopedia states: "He was a disgrace to the Chair of Peter."
Now, why is it, God can use fallible men who may pick the wrong pope (and that pope, in theory, has the power to speak ex-cathedra), yet Akin says God still guides the church, but when it comes to the canon, there has to be an infallible magisterium, or the canon cannot be certain?
Here with the election of a Pope, a Roman apologist like Mr. Akin has no problem that a fallible council of cardinals can pick a pope who might be the wrong choice.
In summary For Romanism:
A fallible assembly of cardinals can pick the wrong pope, and that pope will then have the ability to make infallible statements.
A fallible assembly cannot make a definite statement on the canon (a book of infallible statements).