This was the question dominating Washington punditry in Winter and Spring of 2009.  Political observers knew that Obama would not be able to sustain his approval ratings once the voters began to assign responsibility to Obama for the health of the economy.  They also knew that so long as people viewed the economic collapse as something that Obama had simply inherited from George W. Bush and was trying his level best to deal with, his high approval ratings would remain relatively intact.

The answer to the question now appears to be: four months.

On May 20, 2009, Rasmussen had Obama's overall approval rating at a healthy 58%-41%.  The Rasmussen Index -- which measures strong feelings on the President -- stood at 36% strongly approve to 29% strongly disapprove.

On that day, Gallup measured the President's approval rating at 64% approve, 29% disapprove.  The RCP Average of approval polls similarly had him at 61.2% approve, 32.3% disapprove.

In retrospect, May 20th seems to have roughly marked the end of what had been a pretty stable 3-month run for the President in polls (he quickly and perhaps unsurprisingly lost Republican support in his first month in office).  Since then, attention has focused less on "green shoots" in the economy, and more on the rise in the unemployment rate.  And since then, his approval ratings have steadily dropped.

Rasmussen now has him at a tepid 51%-48% approval, the lowest of his Presidency.  People with strong feelings about the President now lean against him:  30%-38%.  Gallup has his approval at 57%-36% -- up a point from the lowest point of his Presidency yesterday (56%-36%).  And the RCP Average has him at his lowest point ever as well: 56.5% approve to 38.5% disapprove.  This is also in line with polls from Ohio and Virginia showing the President's approval rating slipping below 50% in those states.

To be certain, these are not bad numbers.  They're good.  But they're not the strong numbers from March-May, and they aren't the stratospheric numbers from January-February.  And as more and more people begin to view this as Barack Obama's economy, we can expect more and more people to turn a critical eye toward the President, at least while the economy continues its downturn.

And when you consider that the President's job approval is one of the most important factors in determining how a President's party fares in midterm elections, you begin to understand why we are beginning to hear calls for a second stimulus.  Democrats need the economy to turn around, and they need it to do so fairly quickly if the electorate's perceptions of the economy are going to turn around in time for the 2010 midterm elections.