Pick Dorgan and the reddest state to have 2 blue senators probably gets a red one. I don't know whether Gov. Hoeven would get to pick one, with or without a party limitation, or whether there'd be an election, but the result likely would be an improvement over either Dorgan or Conrad. If Hoeven can pick a GOP replacement he's just been re-elected to his third 4 year term by a landslide, a ND first, so he can afford what ever political hit he'd take for a party switch.
Pick Arnold and the Cal. GOP can start blaming his flawed policies on his pro-Obama tendencies. Plus, by promoting Lt. Gov. Garamendi (D) the Cal. Dems won't have any GOP left to blame for the state of their state.
Good analysis, imo.