[The Saucepan Man]

Folks, take a look at Firefoot's posts.

Tolkien makes it absolutely clear in his Letters that no one in Middle-earth could voluntarily have destroyed the Ring at Sammath Naur. Not Gandalf. Not Aragorn. Not Legolas. Not even Elrond. Galadriel's temptation shows that Elves were not immune to its corrupting influence. The only possible exception, as Firefoot said, was Tom Bombadil as the Ring had no effect on him. But, as Legoals said, he would never have taken it to Mount Doom and, even if he had, it may well have been able to master even him outside his own realm.

Any other analysis would speak terribly ill of Frodo. If someone else had been able to achieve what he could not, then his character would be incredibly diminished. Frodo feels guilt at not being able voluntarily to destroy the Ring, but he has no right to, since no one else could have done it. His heroism derives from the fact that he was able to battle through terrible hardship to bring the thing to the one place where it could be destoyed, and from the pity he showed to Smeagol, which allowed providence (Eru) to intervene at the vital moment.

I doubt that there are many others that would have been able to resist the Ring for long enough to get it to Sammath Naur. But, had Frodo been killed, then my choice for substitute Ringbearer would be another Hobbit, given their peculiar resilience to the Ring's influence. Not Sam, for his strength was in support, and I doubt that he would have shown the pity to Smeagol that Frodo did. So Merry or Pippin would be my choice. Quite possibly Pippin, because he seems the more spiritual of the two, although perhaps Merry is mentally the tougher. In any event, the ideal situation (absent Frodo) would, in my view, have been one of them with the other in support.