The discussion sparked by this question led to a suggestion that I open a separate question on a related subject. Sauron started out good, became bad, briefly repented, the went full-on evil. Saruman too started out as a good guy, but very gradually turned to the Dark Side, so to speak.
I know some of the factors which contributed to his slow decline - jealousy of Gandalf, gradually increasing egotism, corruption at the hands of Sauron via the Palantir, and so on. And I know - in part because of the answers to this question - what Saruman's intentions were during the events of The Lord of the Rings: basically, he wanted to pretend he was Sauron's buddy for as long as it was profitable to do so, steal the Ring, use it to defeat his enemies (including Sauron), and eventually take Sauron's place (which, whether or not this was Saruman's intention, would automatically make him the baddest baddie in Middle-earth).
But I know little (aside from what I have already mentioned above) about what his intentions were from the time he came to Arda to the time Gandalf located the One Ring, how soon they began to change, and why.
What were Saruman's original intentions, how soon did he begin to stray, and what started that process?