The conservative base has to be energized or the south goes into play for the dems. Furthermore, if the dems are encouraged by the fact that the voters have been given a choice between clinton and clinton-lite, then the party activists will know they might be able to get the election close enough to steal thru vote fraud (like they almost did in 2000 after the errant call for Florida before the polls were closed supressed the GOP turnout in western FLA by at least 5000 to 10000 votes).
The northern liberal republicans are counting on the loyalty of the southern conservatives to vote for their liberal candidate, while they scare everybody else into voting for him.