[Child of the 7th Age]

Sam was indeed a staunch hobbit who gave of himself a thousand times over to help Frodo accomplish his mission. Without Sam, Frodo would never have made it as far as he did.

But there's one other point that hasn't been brought up. In his Letters Tolkien makes it clear that no being in Middle-earth could have succeeded in tossing the Ring into Sammath Naur. We are simply too "flawed" in our nature. Even Gandalf, who was a maia, clearly stated that he could not have resisted the temptation of the Ring. This means Sam would also have been tempted in some way or form.

One of the key differences between Frodo and Sam was that the former showed kindness to Gollum above and beyond what any 'normal' person would have done, and it was this showing of mercy which made possible the action of providence on Mount Doom. Sam was different. His strengths were loyalty, steadfastness, and a stubborn endurance that were undoubtedly stronger than Frodo's. But there was also a "down" side. He was insular and suspicious. This is reflected in his earliest encounters with Strider as well as his dealings with Gollum. Tolkien talks about this in his Letters as well.

Some of us would say that Sam was more realistic in his assessment of Gollum, but Tolkien didn't see it that way. He tells us that Frodo's mercy which seemed to go beyond the rational was essential for the story to succeed. Think how much more suspicious Sam would have been if he had actually been bearing the Ring. He would have wanted to protect it against Gollum. I doubt Gollum would have lasted too long. During one of their arguments, Sam would have blasted him away.

There is an irony in this: Sam would have replicated the scene between Deagol and Smeagol that started this whole mess with the Ring and Gollum. It would be another case of hobbit slaying hobbit, and on some level I think Sam sensed that. So the cycle of evil would have been perpetuated by Sam and we'd be right back where we started. Once the slaying was done, Sam's spirit would have been corrupted and there is no way he could have gotten the Ring to Mount Doom, let alone throw it in.

It is easy to point to Frodo's shortcomings. From our easy armchair perspective, he seems to have been tinged with a martyr complex and too often fallen prey to internal pressures, losing sight of hope without enough of a fight. But there's another side here. The amazing thing is that Frodo was able to look at Gollum with a gentler heart, recognizing some of what he'd gone through. It would have been so easy for Frodo to become possessive about the Ring and lash out at Gollum, since the latter so obviously wanted it for himself.

It is not Sam who has the gleem of an Elf friend in his eye or who is becoming like the phial of Galadriel. It is Frodo. Sam recognizes that quality in Frodo and loves him for it. Sam is the good and decent person who sacrifices himself for those he loves in amazing ways. Frodo is the quieter one who can look beyond what we see in everyday human life and get a hint of what lies beyond. This is what makes him able to show mercy when, by any rational earthly standard, he should have clobbered Gollum over the head.