what if Sam had kept the ring?!!!!!

I'd have to agree with everyone who said he'd make it because of his love and devotion to Frodo. 'Good-bye, master, my dear! Forgive your Sam. He'll come back to this spot when the job's done - if he manages it. And he'll not leave you again ... And if the lady could hear me and give me one wish, I would wish to come back and finde you again. Goodbye!' And even if Frodo didn't give Sam the strength to do it, he would be able to make it much easier than Frodo because the ring had no hold over him yet, he would only need food and water for himself, and the purity of his heart would urge him on.