Voters in several U.S. states go to the polls for congressional primary elections Tuesday, and voters in Arizona will elect a replacement for Representative Gabrielle Giffords, a Democrat.

Giffords resigned in January, a year after being shot in the head during a public appearance in Tucson, Arizona. Six people died in the shooting and 13 were injured.

Giffords' former aide Ron Barber, who was one of the injured, is running against conservative Republican Jesse Kelly for Giffords' seat. Whoever wins will serve the remaining six months of Giffords' term, but must run for re-election in November, albeit with a distinct advantage as the incumbent.

Polls show that Barber is benefiting from sympathy for Giffords and is likely to win Tuesday's election.

Primary election voters in Virginia, Maine, Nevada, North Dakota, and South Carolina are selecting candidates to contest congressional seats in November.

With the economy dominating election issues, Barber has vowed to protect federal health care provisions and lower pressure on the middle class with tax cuts. Kelly, who nearly unseated the incumbent Giffords in the 2010 congressional election, has proposed an increase in energy production and encouragement of energy production.

On immigration, an issue important in Arizona, which shares a long southern border with Mexico, Barber wants more agents stationed at the border, while Kelly favors the building of a double-layered fence to keep intruders out.