Aug. 10: Iowa, the Forgotten Swing State

By NATE SILVER

Some swing states get more polling love than others. In Florida, the matchup between President Obama and Mitt Romney has been tested 29 times by pollsters since last November. In Ohio, there have been 25 polls, and in Virginia, 27.

But Iowa? Just nine polls there since November, or about one per month. So we know much less about what's going on there than in the other swing states. But there was a new poll out there on Friday, and it had pretty good news for Mitt Romney.

The survey, from Rasmussen Reports, had Mr. Romney two points ahead among likely voters. This is a base-hit poll for Mr. Romney rather than a home run, since Rasmussen's polls are a bit Republican-leaning and since there wasn't much movement from its prior poll of the state (which had Mr. Romney one point ahead). Still, after a tough week of polling, Mr. Romney should be pleased with any swing-state lead that he can get.

Our forecast still has Mr. Obama as a modest favorite in Iowa, although his probability of winning the state declined to 63 percent from 67 percent on the new survey. Part of the reason is that, in the absence of a sufficient amount of polling, the model weighs what we call “state fundamentals” fairly heavily.

The most important fundamental is simply how the state voted, relative to the national trend, in the past couple of presidential elections. Iowa is typically just slightly Democratic-leaning: it voted for Mr. Obama by 9.5 percentage points in 2008, as compared with his national margin of victory of 7.3 points. Iowa's economy is also fairly healthy, and Mr. Obama has raised about twice as much money as Mr. Romney there. These are factors that have some modest predictive power.

So Iowa should be Mr. Obama's state to lose - certainly if the national race is roughly tied, and more so if Mr. Obama holds a lead of a couple of points nationally. If we see more polls like this from Iowa, it will qualify as a swing state in which he's underperforming.

Mr. Romney also got some decent news from the national tracking polls on Friday. His lead in the Rasmussen Reports national survey held at four points, and Gallup's tracking poll moved back into a tie.

The balance of polling data has still been favorable to Mr. Obama over the past few weeks - but as I wrote yesterday, it's very unlikely that there has been some sort of sea change in the race. And Friday was one of Mr. Obama's weaker polling days in some time, albeit on a thin volume of surveys. Mr. Obama's chances of winning the Electoral College declined to 72.0 percent in the forecast, from 73.3 percent on Thursday.