Why Ariz. Sens. Kyrsten Sinema, Mark Kelly will be key to the immigration reform debate on Capitol Hill

During the last serious attempt at an immigration overhaul, Sens. John McCain and Jeff Flake played pivotal roles.

McCain and Flake, both Arizona Republicans, were members of the bipartisan "Gang of Eight" that hashed out a sweeping immigration reform deal that would pass the Senate in 2013. They were the only senators in the group from a border state.