TUCSON, Ariz. -- First Lady Michelle Obama paid tribute to Gabrielle Giffords at a campaign event Monday night -- and pledged her confidence in the former aide running to replace the wounded congresswoman.

Addressing the fundraiser at the Tucson Convention Center, Obama saluted Ron Barber, who was Giffords' district director, saying, "He is going to do a fantastic job representing his district in Washington."

The first lady also noted that Giffords' mother, Gloria Giffords, was present -- and told her that both she and husband Barack Obama are inspired by the lawmaker's determined recovery from the shooting rampage that left her with serious brain injuries in January, 2011.

"We love her and are with her, with you, with the family every step of the way," Obama said.

Giffords and Barber were among 13 people wounded in the Tucson shooting, which left six people dead. Accused gunman Jared Lee Loughner, who struck as Giffords met constituents, is undergoing mental health treatment as his case continues before the courts.

Giffords said in January this year that she would resign from the US House to focus on her rehabilitation.

Barber announced his candidacy to serve the remainder of her term, which expires next January, and will face GOP candidate Jesse Kelly in a June special election. Both parties will then hold primaries to pick candidates for the November general election.

Looking to November, Obama told Tuesday's 450-strong audience, "I know we are going to do it here because of people like you."

Touting her husband's policies, according to a pool report for FOX News Channel, she said voters will be making a choice that impacts the lives of people for decades to come.

"The choice we make will determine nothing less than who we are as a country, but more importantly, who we want to be," Obama said. "Will we be a country where opportunity is limited to just a few at the top? Or will we be a place where if you work hard, you can get ahead no matter who you are or how you started out?"

Rounding off her 25-minute speech, to a standing ovation she asked, "Are you in?"

"I know so well what the stakes are ... We need you every step of the way."