Obama has lost in two key groups — progressive Democrats and blacks — who helped put him over the top in 2008.......The percentage of liberal Democrats strongly supporting Obama’s job record has fallen 22 points, from 53 percent last year to 31 percent now. And the number of blacks believing Obama has helped the economy has tumbled from 77 percent in October to just more than 50 percent, the Post reported.

Even here in the bluest Cesspool,Massachusetts, some of President Obama’s stalwarts say their support for the liberal darling is slipping — as a new poll suggests the numbers are plummeting in the president’s base and a call has emerged from the left for a primary challenge.

“Our expectations were high, and the disappointment started happening early and often,” said state Rep. Denise Provost (D-Somerville), a big backer in 2008, now bothered by Obama’s snub to Harvard professor Elizabeth Warren and his extension of tax breaks.

“He needs to stop spending money on the war and sending our youth overseas, and stop spending our money to kill other people,” said Mel King, a progressive community activist and former Boston mayoral candidate, who said he has become disillusioned by Obama’s decision to continue the war in Afghanistan. “That’s one issue that I think he really needs to step up on.”