Confirming the pattern Zogby points to is Rasmussen, graph above from this page.
More from Rasmussen's Daily Presidential Tracking Poll, dated Sept. 1, 2009:
The Rasmussen Reports daily Presidential Tracking Poll for Tuesday shows that 30% of the nation's voters Strongly Approve of the way that Barack Obama is performing his role as President. Forty-one percent (41%) Strongly Disapprove giving Obama a Presidential Approval Index rating of -11 (see trends).
Obama's decline continues at a rapid rate.
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