[Nikkolas]

Of course the Ring isn't exactly Sauron himself. The palantir was a direct link to Sauron unmasked - his will and his mind and Saruman could not conquer such strength. The Ring though obviously does not have nearly the same level of overt power or else Frodo would have been driven mad long ago.

I just think that Saruman using his innate power and his will to dominate others (which is a factor for mastering it according to Galadriel) could potentially claim it for himself. Note also that it is specifically Gandal's Maia nature that Tolkien attributes to his ability to take the Ring and challenge Sauron. Saruman thus fulfills some of the know criteria for mastring the One and using it.

I cannot help but think Saruman's losing his "mental battle" with Sauron via the palantir is due to how similar they are in mind. In Fellowship I believe it is Gandalf who says that even against the might of the One Ring you can at least temporarily fend it off if you have a noble character. Maybe it was a similar situation with the Stones. So Saruman, even if he is weaker than Sauron, might not have been "ensnared" by him if he had righteous cause for using the Stone. As it was though, he was essentially a lesser Sauron and thus naturally his mind was more easily swayed and dominated by his "superior self" if you get me.