In Debian-derived Linux distros, if you are not root but are authorized in /etc/sudoers, GNOME will ask you for your own password to allow privileged operations.
However, Scientific Linux asks you for the real root password, even if you can do the same action with sudo. A Google search suggests this is true for all Red Hat or Fedora-derived distros, but the suggested solutions are all very old, complex, or not very complete.
How should I configure GNOME, gksu, kernel PAM, polkit/PolicyKit, or what-have-you to let me use sudo properly within the GNOME GUI?