Tacitus has some thoughts on state legislatures vis à vis political parties and the liberalism-conservatism scale. It's an interesting piece as far as it goes, but it begs a couple of empirical questions:
Why do Republicans fail to compete effectively for the median voter in "liberal" states? Democrats in the South seem able to separate themselves from the national party, yet this eludes Republicans. Is it simply a matter of gerrymandering or incumbent advantage? (Some political scientists would argue that on the "local" issues Dems have the advantage of the right issue positions, though; no state legislator is ever going to have to vote on defense or national security, two Republican-"owned" issues, to borrow from John Petrocik.)
Why does Democratic control of state legislatures persist in states that elect Republicans regularly to national office?
Some people have gotten at corners of these questions (and I'd cite them if I could remember them offhand; the realignment literature is an interesting place to start), but I don't think there's been a good answer yet. And a good answer might actually be relevant to the real world, something us PoliSci people are rarely good at providing.