People sign up with "Ready for Hillary" during former U.S. Secretary of State Hillary Clinton's book signing event for "Hard Choices", outside a Costco store in Arlington, VirginiaPeople sign up with "Ready for Hillary" during former U.S. Secretary of State Hillary Clinton's book signing event for "Hard Choices", outside a Costco store in Arlington, Virginia People sign up with "Ready for Hillary" during former U.S. Secretary of State Hillary Clinton's book signing event for "Hard Choices", outside a Costco store in Arlington, VirginiaHillary Clinton signs copies of her book "Hard Choices" at a Costco store in Arlington, Virginia