In the comments below a weird fact came to light: it does not seem that liberal/Democrat reduced skepticism toward astrology vs. conservatives/Republicans can be explained just by a secularization, and therefore diminished Christian orthodoxy. There are two reasons for this. First, on a priori grounds most people are religious, liberals and conservatives. The difference between the religious and irreligious on this issue would have to be rather large, and the different apportionment across ideology to be striking, for it to drive the division which seems so robust. Second, within the results it seems rather clear that the gap between liberals and conservatives is most evident amongst the religious of both! In other words, secular liberals and conservatives tend to agree (and be skeptical) in relation to astrology. While religious conservatives are skeptical of astrology, as one would expect from orthodox conservative Christians, religious liberals are not. The table below shows some results.
Observe the huge difference between Creationist and fundamentalist liberals and conservatives!