As for Sanders, given the two-party system, I would expect a senator left of the Democrats to mostly vote with the Democrats just as I would expect a senator to the right of the Republicans to mostly vote with the Republicans. We need more political parties on the left, right, and center, but I don't think limited options makes him a false independent. As for King, he's only got a few months of a voting record, but it makes sense to caucus with the majority given the choice.
Left right and center are mostly party constructs. Political ideology is infinitely more complicated than that, but the idea of left, right, and center make it easier to lump your beliefs nicely with those of others, which is necessary for a party system. In reality a politician can be in favor of regulating the oil industry and against regulating the communications industry; there is not hypocrisy there.
