Saturday, October 20, 2012

Let's Say Rasmussen is Right

Rasmussen is not a terrible pollster but you have to understand what Rasmussen is doing in order to interpret their results.

First, Rasmussen is a robo-pollster. They don't do live-interviewer polls and this means they also don't call cell phones. This is one reason why Rasmussen has a bit of a Republican lean. In general, Nate Silver has argued Rasmussen has about a 2-point Republican lean. Their national tracking poll currently has Romney ahead by 1 point (49/48). So, a 2-point lean would put Rasmussen right about where some other national polls are.

Second, Rasmussen weights by party ID. This has two implications for how we read their polls. First, Rasmussen's polls are going to be less volatile than other polls. When something happens that changes public attitudes about the race, poll respondents don't just change their response on which candidate they support. They also sometimes change their response on their party identification. If you have a fixed number of Republicans and Democrats you're looking for in your poll, you are not going to pick up that shift even though it is real.

How does this play out? Since late September, most pollsters have shown a shift towards Romney in the national polls and, more recently, a tiny shift back towards Obama. Rasmussen's national tracking poll has remained within a very narrow range between Obama ahead by 2 and Romney ahead by 2. For the last couple of weeks, Rasmussen's tracker has been within an even more narrow range between a tied race and Romney ahead by 2. These same things are true at the state level as well: Rasmussen polling is very stable and has a slight Republican lean.

So, let's say all of Rasmussen's polls are right. Who wins? It looks like Obama wins.

Rasmussen's "Electoral College Scoreboard" has Obama ahead in states totalling 237 electoral votes and Romney ahead in states totalling 235 electoral votes. 7 states are listed as tossups. But Rasmussen has done polling in these tossup states (very recently in most of them). Here's what those numbers show:

CO - Obama +1
IA - Obama +2
NH - Obama +1
NV - Obama +3
OH - Obama +1
VA - Romney +3
WI - Obama +2

All of these polls are very close but Obama is winning in more than enough of them that if Rasmussen is right, Obama wins. If Nate Silver's arguments about Rasmussen's lean is right, Obama wins a bit more handily.

Again, we come to the same place: Is it close? Yeah. Is Obama winning right now? Yeah.

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