Though I hold substantially less esteem for Senator Spector since he left the GOP, it must be said that being a moderate ain't much fun these days.
As difficult as it is to be a moderate Republican, the gods of politics do not look favorably upon party-switchers. He would have been better off fighting to the bitter end in the GOP primary and at least being a standard-bearer for the dwindling numbers of voters who long for statesmenship and virtue instead of ideological madness and vitriol.
He probably should have just switched to Independent. He would have had a better chance in a three way race.