In 2008, Barack Obama summed up his case against Republicans with the slogan "Had Enough?" In 2012, Republicans could take back the White House with the slogan "Not Enough."

Since January 2010, the U.S. has added more than 4 million private sector jobs, the economy has grown, if slowly, in every quarter, and the unemployment rate has fallen by 1.5 percentage points. But it's been not enough -- too little, too slow -- and President Obama's approval rating for the economy is no higher than it was two and a half years ago.

The graph below shows public approval of Obama's handling of the economy since February 2009. The long story made short is that the burst of optimism after Obama's election faded as the economy shed 4 million jobs in the president's first year in office. Since then, it's been a steady erosion of support until the end of last year. Today's NYT/CBS poll finds economic approval slipping again.

Here's the same graph as above, overlayed with the economy's most visible and talked-about indicator: the unemployment rate, whose axis is on the right. The relationship, if one exists, is hard to see. A falling unemployment rate has been too little, too slow, and not enough to stem the flood of support for the president's economic policies.

Here's the same graph, this time comparing only economic disapproval and the unemployment rate. You might expect that disapproval and unemployment would fall in tandem, as celebrated jobs reports drove up approval of the administration. But the rate of recovery has been so slow that even small positive numbers have failed to inspire confidence in the White House.

If you cut off the first two years of Obama's term to focus on the recent past -- not that I'm suggesting voters have short memory spans, of course -- Obama's economic approval/disapproval looks remarkably consistent. The confidence gap hovers around 10 or 15 percent, breaks open after our awful 2011 summer, and closes after a series of strong jobs reports. Now we're back near 15 percent.