More than half of political independents — 53 percent — say Obama’s explanation that he learned it from media reports is untrue, while 34 percent say they believe him.

“How could he not know?” said poll respondent June Wilshusen, 50, of Yuma, Colorado, a political independent and a stay-at-home wife married to a machinist. “I think any president has to know what’s going on with our government. I think they’re very aware of the IRS.”

The doubts about Obama’s credibility come as a series of scandals have dominated news coverage, helping to diminish a post-election surge in the president’s popularity and optimism about the direction of the country. Obama’s job approval rating declined six percentage points since the last Bloomberg poll in February, to 49 percent from 55 percent, returning to its lowest level since last September…

The president’s personal popularity has been more resilient. Fifty-three percent of Americans say they have a favorable impression of him, down from 56 percent who said so in February.