Louisiana adopted this around 1979. Before the open primary, Louisiana was a one party state (Democrat). The then governor, Edwin Edwards, thought the open primary would eliminate his perceived problem of the Democrats beating each other up, then the bloody winner having to face a fresh Republican. The end result was to enable Louisiana to become at two party state.
I really like the result.
The outcome of this poll is just what I would expect coming from California the land of Bizarro World