Sen. Jeff Flake (R) decided to retire because of the direction of the Republican Party under President Trump. Three Republicans are fighting for nomination to his open seat. They are Rep. Martha McSally, who was the first female U.S. fighter pilot to fly in combat, conservative former state senator Kelli Ward and controversial former sheriff Joe Arpaio. McSally has moved to the right on immigration during the campaign.
The likely Democratic nominee is Rep. Kyrsten Sinema, a former Green Party activist who has become more centrist over the years.