I think Sam wouldn't have the conviction to get things done. He wasn't the one who stood up and accepted the ring at the council. Sam was loyal and didn't have lofty desires, but he didn't have the spirit of adventure and perseverance that Frodo had. He was the perfect ally to help Frodo, but he wouldn't have made a good Ring bearer himself.

Unless Tolkien addressed this in one of his letters (I really wouldn't be surprised), we don't know for sure, but my guess would be that Sam's resistance was mostly temporary. He could carry it for a short while without succumbing, and he could be around frodo for the whole journey with no issue, but he'd have eventually succumb to it.

Also worth noting that it's heavily implied that the whole thing was predestined by Eru, and so with that in mind, it makes perfect sense that Frodo carries it instead of Sam, because

A) if Sam carried it, it's unlikely he would have trusted Gollem, and his "help" was required in several ways to get the job done

B) Frodo being the carrier + Sam as his sole ally, while not intended by the council of Elrond, turned out to be a formidable match, thanks to Sam's resistance to the ring and his loyalty to Frodo. Idk if when push came to shove, Frodo would have been quite as loyal to Sam as Sam was to Frodo (not with the ring doing it's thing afterall.

Its also worth noting that Tolkien had some kinda weird views about the whole "servant & landed gentry" dynamics, as can be seen in just about every dialogue between Sam and Frodo lol - Sam being the effective leader, despite being a humble gardener and Frodo being basically a Lord in hobbit terms isn't something Tolkien was likely to write

Not entirely. Sam was tempted, and if he possessed the ring long enough he would have been overcome like any other, but his Hobbit-sense saved him in that one small moment:

""As he stood there, even though the Ring was not on him but hanging by its chain about his neck, he felt himself enlarged, as if he were robed in a huge distorted shadow of himself, and vast and ominous threat halted upon the walls of Mordor..."

"Wild fantasies arose in his mind; and he saw Samwise the Strong, Hero of the Age, striding with a flaming sword across the darkened land, and armies flocking to his call as he marched to the overthrow of Barad-dur... He had only to put on the Ring and claim it for his own, and all this could be. "

"In that hour of trial it was the love of his master that helped most to hold him firm; but also deep down in him lived still unconquered his plain hobbit-sense: he knew in the core of his heart that he was not large enough to bear such a burden, even if such visions were not a mere cheat to betray him. The one small garden of a free gardener was all his need and due, not a garden swollen to a realm; his own hands to use, not the hands of others to command. "

In the book, when he was carrying it temporarily for Frodo, the Ring did tempt him. He saw himself at the head of a vast garden, a garden rivaling nations, one that would be free of society and allowed to grow endlessly. The feelings of conquest were justified immediately by the retaking of nature.

Not too bad of a temptation, I dare say.