Historical Premature Ejac---er---speculation

Hey, I know he's a favorite whipping boy of a good many in the historical "profession." But this observation by Victor Davis Hanson is a truism, like it or not (via Dale Light).

Critics are not allowed to stop history at a convenient point — at Abu Ghraib, the pull-back from Fallujah, or the bombing of the dome at Samara — and then pass final judgment whenever they wish. If Lincoln had quit after Cold Harbor, Wilson after the German Spring offensive of 1918, or Roosevelt after the fall of the Philippines, then their presidencies would have failed and the U.S. today would be a far weaker — or perhaps nonexistent — country.

History instead will assess Iraq when it ends. {emphasis added}

When historians pass judgment on contemporary or ongoing historical moments, isn't there a temptation to shape the narrative so that it continues to fit their prediction? Remember when George W. Bush was picked as the worst president ever? Or how about Harry Truman? Time and considered evaluation--some would even call it revisionism!--have a way of changing the contemporary conventional wisdom into the opposite.