The only people who like him are Republicans and other "Democrats" who are just registered Democrats but really Republicans and probably would vote for Bush anyway.
And the south is full of, what? Miller is a moderate. He'll campaign for Bush down there to get the base fired up and win over some other moderates. Miller is VERY, VERY popular down there. If Miller goes around in North Carolina, Northern Florida, Luisiana, Georgia, Virginia, Tennessee and West Virgina, then Bush won't have to spend much time at all, if any in those states. That's time and effort (and money) that Bush can spend in other states.
Would he have to spend time there anyway?