This article has a chart that has poll results for “never heard of” various candidates. In every case, more Democrats have not heard of a Democratic Presidential candidate than Republicans. Best of the Web attributes this to Republicans being more politically aware, but it may just be for this cycle.
I suspect that it’s similar to the stock market watching phenomenon. The Republicans are in a bull market politically, so they’re paying attention. Democrats, on the other hand, are enduring a very bearish political market and so they’re tuning out. It looks to me that if the Republicans can get their base out, President Bush is going to have a lot of coattails.