Rep. Gabrielle Giffords, a moderate Democrat, takes her place between Rep. Jeff Flake, a conservative Republican, and Rep. Raul M. Grijalva, a liberal Democrat. Colleagues started a tribute last year by sitting with members of the other party. (Associated Press)

Rep. Gabrielle Giffords, a moderate Democrat, takes her place between Rep. Jeff Flake, a conservative Republican, and Rep. Raul M. Grijalva, a liberal Democrat. Colleagues started a tribute last year by sitting with members of the other party. (Associated Press)