Who’s really leading in Iowa?

It’s hard to imagine anyone thinking that Iowa voters’ party affiliation this time around won’t be at least somewhat to the right of where it was in 2008 — in other words, somewhere to the right of a 1-point Democratic edge. How far to the right of that is harder to guess. But if we assume that party affiliation is dead-even nationally — which is slightly to the left of what Gallup indicates (Gallup shows Republicans with a 1-point edge) — and if we assume that Iowa’s party-affiliation split will again be 6 points to the right of the nation as a whole, that would mean a GOP turnout advantage in Iowa of 6 points this time around. If, however, Iowa is only half as far to the right of the nation in 2012 as it was in 2008 (so, 3 points), or if it remains about 6 points to the right but Democrats actually have, say, a 3-point edge nationwide in party affiliation (meaning Gallup is underselling Democrats by 4 points), then the GOP edge in party affiliation in Iowa would be about 3 points.

Either way — whether Republicans will have a 3-point or 6-point edge in turnout in Iowa (or even anywhere between 2 and 7 points) — that’s pretty close to Rasmussen’s projection of a 4-point GOP edge in turnout, and it’s a long way removed from the projections from NBC/WSJ/Marist (Democrats by 3) or Gravis (Democrats by 6).