Although strongly urged by moderates to sign the Civil Rights Act of 1866, Johnson broke decisively with them by vetoing it on March 27. In his veto message, he objected to the measure because it conferred citizenship on the freedmen at a time when 11 out of 36 states were unrepresented in the Congress, and that it discriminated in favor of African Americans and against whites. Within three weeks, Congress had overridden his veto, the first time that had been done on a major bill in American history. The veto, often seen as a key mistake of Johnson's presidency, convinced moderates there was no hope of working with him. Historian Eric Foner, in his volume on Reconstruction, views it as 'the most disastrous miscalculation of his political career'. According to Stewart, the veto was 'for many his defining blunder, setting a tone of perpetual confrontation with Congress that prevailed for the rest of his presidency'.