Throughout America's history dominance of one of the three branches has essentially been a see-saw struggle between Congress and the president. Both have had periods of great power and weakness such as immediately after the Civil War when republicans had a majority in Congress and were able to pass major legislation and shoot down most of the president's vetoes. They also passed acts to essentially make the president subordinate to Congress, such as the Tenure of Office Act. Johnson's later impeachment also cost the presidency much political power. However the president has also exercised greater power largely during the 20th century. Both Roosevelts greatly expanded the powers of the president and wielded great power during their terms.