We find out that Lauderback had become more inclined to run for the Westland seat when he learned that Crosbie was living there.
Having believed that Crosbie was also Carver's brother (and complicit in the blackmail plot through which Carver had taken over the Godspeed), Lauderback was surprised to get a letter from Crosbie that basically proved Crosbie had had no idea about the plot.