Florida Republican Gov. Charlie Crist is in an unusual situation. He has to choose an interim replacement for Republican Mel Martinez, who will soon resign the Senate seat that Crist previously announced he will seek in the 2010 election.

Charlie Crist (CQ/Scott J. Ferrell)

Some political risk attaches to the appointment: Crist faces a determined challenger in the 2010 Republican primary from state Rep. Marco Rubio, who is running as a more faithful conservative than the governor. Martinez’s successor will serve for about 16 months, and Crist’s choice could signal how the governor would act or vote as a senator himself.

That got me wondering: are there other cases in which a governor made an interim appointment to a Senate seat that he or she was already making plans to seek?