After clearing up some missing-data registration problems for Linn County from 2000 with the Iowa Secretary of State's office (thanks, Phyllis!), I have total comparative data for Iowa registrations between the final, 2000 registration counts and the totals as of September 30, 2004. (If that date sounds familiar to you, it was the day Kerry opened a can of debating whoop-ass on Bush in Miami.)
Anyway, in 2000, the Democrats had 553,744 total registrants statewide (30.4% of all registered Iowans), to 580,219 for the Republicans (31.9%). That made for a statewide, two-party Democratic share of 48.8% -- i.e., as a share of DEM+GOP registrants - with the GOP enjoying a 26,475 registrant advantage overall.
Al Gore, you may recall, carried Iowa by a mere 4,144 votes - and that coming despite not only the registration disadvantage cited in the previous paragraph, but also despite the fact that Republicans turned out their registrants at about four percent higher rate statewide, according to the IA election data.
As of September 30, 2004, the Democrats have 581,675 total registrants statewide (30.7% of all registered Iowans), to 591,000 for the Republicans (31.2%). That makes for an updated statewide, two-party Democratic share of 49.6% of registrants, with the GOP now enjoying only a 9,325 statewide registrant edge. The Democrats are almost at partisan parity, at least in terms of registration.
In sum (so to speak), it's not by leaps and bounds, but the Democrats have gained slightly during the past four years. So our hats are off to all the paid, volunteer and other canvassers working hard in Iowa.