Saruman for or against Sauron?

Originally Posted by Raynor

True, but that didn't seem to matter much to Gandalf in the quote above.

However, he was much weakened and affected by his contest with Sauron. I expect that Saruman would find out about that one way or the other - spies, rumors, Sauron himself, the palantir.

As for your first point, it did matter to Lady Galadriel. Secondly, the LOTR clearly states that Denethor was most displeased with the Ring going to Mordor. He wanted it in Minas Tirith, to be used only at the uttermost end of need. So there is not a case to say he was too weak or had no desire to wield the Ring. The only question in his mind was, who should wield it?