Is Baldwin a libertarian? Who knows.
What I have seen of libertarians: They weasel into conservative circles once Republicans are in power because we share the ideals of small government. Then around election time, they come out hard against Republicans so they can run their little stinky party ideology which happens to hate conservatives and Republicans and try to split the GOP. When the GOP is weak among conservatives, they shout "vote third party" as if this is going to enhance the power of conservatives. I call them miners.
I think Baldwin is a libertarian - a miner for division.