Pres. Obama's approval rating is down 10 percentage points over four months. The decline has been steady and across all groups. (For example, while Democrats are still much more favorable to Obama than Republicans, the decline has been almost equal in percentage points within each partisan group. Independents too. Some numbers on that just below.)

According to the Pew Research Center, the portion of Americans who said they approve of the way Obama is performing his job has dropped from 62 percent in April to 52 percent in late August while disapproval has increased from 26 to 37 percent.

Pollster.com, which aggregates polls from many sources, shows Obama with an average approval/disapproval of 50.9/43.9. I know of no reason to assume that it has bottomed out. If you look at this graphic from pollster.com the lines do appear to be flattening slightly (meaning a possible halt to the Obama slide) but more data would be needed to reach that conclusion.

Polysci superguru Larry Jacobs says that Obama could be at a "tipping point," meaning that one possibility is that his standing with the public falls seriously off a cliff in the period just ahead.

The above 60 percent approval rate that Obama maintained during the first months of his term was very high and surprisingly stable for those roughly four months, Jacobs said. That makes the descent to the low 50s look sharper, but such a rating by itself is not cataclysmic, he said. Pres. Bush (II) had similar numbers during his first year until the rally-round-the-prez effect after the 9/11 attacks sent Bush's  ratings into the stratosphere.

But approval ratings of barely 50 percent (below that in a few of the polls aggregated by Pollster.com) are not good, even if they are not unprecedented. Jacobs said that political science circles, Obama's sagging popularity are taken to be "impersonal," meaning they don't have much to do with anything Obama is saying or doing and more to do with the fact that the economy is so bad. Jacobs said the health care debate that dominates the news "isn't helping" Obama, but the main thing dragging him down is the economy.

Obama still has a plurality of approvers among independents (in the Pew August numbers its 48/40). The big sign that Obama's ratings are falling off the cliff will be that the independents are abandoning him, Jacobs said.

Below is the email from Andrew Kohut of Pew that set me off on this post, and there's a link at the bottom of it to the details of Pew's April and August approval ratings for Obama in more detail (if you click through to that table, and look at the last column which shows the April-august change by group, you'll be impressed with consistent the level of decline is across the groups):

In April, 62% of the public approved of Barack Obama's performance as president and 26% disapproved. In August, just four months later, 52% approved of Obama's job performance while 37% disapproved.

Obama's approval rating has declined across nearly all major demographic and political groups: It has fallen 11 points among women and nine points among men; by 12 points among Republicans, 10 points among Democrats and nine points among independents.

For a detailed breakdown of the changes in Obama’s job approval ratings, based on 3,013 interviews in April and 4,013 interviews in August by the Pew Research Center for the People & the Press, click here.