Arizona Senate Seat Primary Today

Rep. Jeff Flake a front-runner to replace Jon Kyl.

Republican voters in Arizona are set to pick a nominee on Tuesday to replace U.S. Senator Jon Kyl, who is stepping down at the end of the year, with conservative Representative Jeff Flake favored to win.

Flake was leading by a huge margin in opinion polls over Wil Cardon, a feisty political newcomer with deep pockets, in a primary election for a seat that Republicans need if they are to have a chance to take control of the Senate in the November election.