[Lord Elrond]

Okay I just caught up on all the posts since yesterday and I guess it all comes down to exactly what you define as a spiritual connection. Yes I believe the ring corrupted Frodo to have more things go on inside him that have characteristics of the dark Lord because the ring was controlling him. So it wasn't actually Frodo and Sauron who had a spiritual connection but the ring through Frodo and Sauron that had the connection. I think once the ring was destroyed there were afteraffects that took a while to go away but more of it was Frodo's senses having a hard time controlling his mind after having little to no control for so long.
As far as Frodo having connections with Gollum yes I believe the pity he had toward him was due to them both being of an estranged and far removed kindred and Frodo and Gollum both posessing the ring but as far as sharing that feeling with Sauron absolutely not. Sauron and the ring were one. The ring did not control Sauron it was him. Sauron came then put himself into the ring so there were no feelings of control over Sauron. He needed the ring to live. The ring overpowered all other bearers mind wanting them to need it and be enslaved to it(for all basic purposes). Frodo and Gollum didn't need the ring to live Saurons life force itself was bound to the ring. They are two totally different connections.