Pew: Obama has big lead; Romney favorability drops (Updated)

New polling data out from Pew Research Center finds President Obama with a double-digit lead over Mitt Romney nationally:

Currently, 51% say they support Obama or lean toward him, while 41% support or lean toward Romney. This is largely unchanged from earlier in July and consistent with polling over the course of this year. Across eight Pew Research Center surveys since January, Obama has led Romney by between four and 12 percentage points. Obama holds only a four-point edge (48% to 44%) across 12 of this year’s key battleground states. While the data does not allow a state-by-state analysis, the overall balance of support in these closely contested states has remained level in recent months, with Obama slightly ahead, but neither candidate holding a significant advantage.

The poll also finds that Romney's favorability has taken a hit this summer:

By a 52% to 37% margin, more voters say they have an unfavorable than favorable view of Mitt Romney. The poll, conducted prior to Romney’s recent overseas trip, represents the sixth consecutive survey over the past nine months in which his image has been in negative territory. While Romney’s personal favorability improved substantially between March and June – as Republican voters rallied behind him after the primary season ended– his image has again slipped over the past month. Barack Obama’s image remains, by comparison, more positive – 50% offer a favorable assessment of the president, 45% an unfavorable one. Even so, Obama’s personal ratings are lower than most presidential candidates in recent elections.

The 10-point lead for Obama here is bigger than any of the other recent polling we've seen, which have tended to show a fairly static race.

(Also on POLITICO: Democratic voter enthusiasm is down)

UPDATE: We've been getting emails from readers pointing out that the sample of the poll is skewed toward Democrats. This is a fair point: the poll does sample significantly more Democrats than Republicans. As I noted above, these results are different than the mostly static numbers we've seen so far -- the sampling numbers explain why.