Would the Nazgul, arriving at the Cracks of Doom have switched their allegiance to the new self-proclaimed lord of the Ring, Frodo Baggins? According to Tolkien, because Sauron still held their rings and controlled their wills 'they would have obeyed or feigned to obey any minor commands of his (Frodo) that did not interfere with their errand... That errand was to remove Frodo from the Crack.... They would have greeted Frodo as 'Lord'... and induced him to leave Sammath Naur... to look upon his new kingdom...' (ibid, letter #246).
Samwise, in his innocence, saw through the chimeric fantasy of "Samwise the Strong, Hero of the Age, striding with flaming sword across a darkened land... and at his command the vale of Gorgoroth became a garden ...he knew in the core of his heart that he was not large enough to bear such a burden... The one small garden of a free gardener was all his need and due..." ("The Lord of the Rings", Book six, chapter I, 'The Tower of Cirith Ungol')
If Gollum was removed from the scene, would the task of seeing the quest through have fallen to Sam? With the Nazgul frantically winging their way to Mount Doom, Sam would have had little time to debate with Frodo about the prudence of destroying the Ring. (Not that a last minute appeal to Frodo's hobbit-sense would have done much good. Frodo, by that juncture, was beyond rational thought.) Would Sam, with the Nazgul entering Sammath Naur, have then sacrificed himself and his beloved master by grabbing Frodo and throwing themselves into the Fires?
If Frodo had had even a moment, he would certainly have been enticed with a powerful new temptation, one very much like that presented to Samwise when he wore the Ring - to become the new Lord of Barad-dur.
Imagine the opportunity: to be able to right age-old wrongs and set evil on its head, to bring peace to Middle-earth. With the resources of Sauron's empire at Frodo's beck and call, he could achieve great things.
