  The TeV blazar PKS 2155--304 was the subject of an intensive 2 week optical
and near-infrared observing campaign in 2004 August with the CTIO 0.9m
telescope. During this time, simultaneous X-ray data from RXTE were also
obtained. We compare the results of our observations to the results from two
previous simultaneous multiwavelength campaigns on PKS 2155-304. We conclude
that the correlation between the X-ray and UV/optical variability is strongest
and the time lag is shortest (only a few hours) when the object is brightest.
As the object becomes fainter, the correlations are weaker and the lags longer,
increasing to a few days. Based on the results of four campaigns, we find
evidence for a linear relationship between the mean optical brightness and lag
time of X-ray and UV/optical events. Furthermore, we assert that this behavior,
along with the different multiwavelength flare lag times across different flux
states is consistent with a highly relativistic shock propagating down the jet
producing the flares observed during a high state. In a quiescent state, the
variability is likely to be due to a number of factors including both the jet
and contributions outside of the jet, such as the accretion disk.
