We have to look at polling data to get a nationwide picture of party affiliation. Interestingly, it also shows an 8% Democratic lead in 2000. Harris polling from 2004 shows the Dem edge to have shrunk, but I would like to see more recent figures. I suspect it may have returned to pre-Bush levels.
U.S. adults are still almost equally divided between Democrats (34%) and Republicans (31%), with the Democrats maintaining a very small advantage. One quarter of all adults consider themselves Independents.
These are some of the results of Harris Poll surveys of a total of 10,012 U.S. adults conducted by telephone by Harris Interactive® between January and December 2004.
The Harris Poll® also found that conservatives continue to outnumber liberals by 36 to 18 percent but that the largest number of people think of themselves as moderates (41%). The remarkable thing about these numbers is how little they have changed over the past 30 to 40 years. Harris Interactive data over four decades show that the average numbers of moderates have remained at 40 or 41 percent, and that conservatives have only varied between 32 and 38 percent, while liberals have remained at a steady 18 percent since the 1970s.
However, the long term trend for party identification has changed over the last 40 years, with the Democratic lead declining from 21 percentage points in the 1970s, to 11 points in the 1980s, seven points in the 1990s, and (so far) five points in this decade.
http://www.harrisinteractive.com/harris_poll/index.asp?PID=548