But by the turn of the 20th century, white historians, led by the Dunning School, saw Reconstruction as a failure because of its political and financial corruption, its failure to heal the hatreds of the war, and its control by self-serving Northern politicians, such as those around President Grant. Historian Claude Bowers said that the worst part of what he called "the Tragic Era" was the extension of voting rights to freedmen, a policy he claimed led to misgovernment and corruption. The freedmen, the Dunning School historians argues, were not at fault because they were manipulated by corrupt white carpetbaggers interested only in raiding the state treasury and staying in power. They agreed the South had to be "redeemed" by foes of corruption. Reconstruction, in short, was said to violate the values of "republicanism" and all Republicans were classified as "extremists". This interpretation of events, the hallmark of the Dunning School, dominated most U.S. history textbooks from 1900 to the 1960s.