PHOENIX – Ron Barber was always the behind-the-scenes man for his boss, Arizona Rep. Gabrielle Giffords.

Then he was shot, when a gunman opened fire on the congresswoman and others at a Tucson grocery store as Barber ushered constituents to meet her. During the year since, he became one of the most visible faces of the tragedy.

Now, he’s taking one more step into the spotlight, asking voters in Giffords’ southern Arizona district to elect him to replace her in Congress after she stepped down last month to focus on recovering from a gunshot wound to the head.

Barber announced Thursday that he will seek the Democratic nomination in the special election being held this spring.

He said he hasn’t decided yet if he’ll seek a full two-year term in November.

Giffords asked him to run in the special election, he said. She and her husband, former astronaut Mark Kelly, endorsed him and asked supporters to donate to his campaign, saying “Ron is a leader who puts politics aside and brings people together.”

The endorsement could help Democrats keep the seat because many in the district hold both Giffords and Barber in high regard, said William Dixon, a University of Arizona political science professor.

“The Republicans are going to have a real hard time with this endorsement,” he said.