Roosevelt's attempt to "pack" the Supreme Court proved extremely costly to FDR and to the New Deal because
a) the Court members he appointed still failed to support him and the New Deal
b) Congress began proceedings to impeach FDR so his momentum decreased
c) in an age of dictators, it made him seem like he was willing to violate separation of powers to become powerful
d) After his failed attempt, the Supreme Court declared many of his New Deal programs unconstitutional.