More like "still a Democrat."
"Independent thinking" is defined by Democrats as "thinks like a Democrat." There are few parties more monolithic in their policies than the Democrats. Ask Leiberman what happens to actual Democratic "independent thinkers."
Spector didn't change on principles. He changed because he was going to get his ass handed to him in the Republican primary, and he thought he'd at least have a better shot with the Democratic primary.
That was then, this is now