Barber announced in February he was running in a special election to finish the term for Giffords, who stepped down in January — one year after both she and Barber were injured in a shooting spree in her district.

A handful of Democratic candidates were eyeing the seat, but they stepped aside out of deference to Barber, who said he hadn’t decided whether to also run for the full term that starts in 2013.

Anticipating that Barber would carry out the rest of Giffords’s term and then bow out, the Democrats set their sights on the fall.

One month later, Barber announced he would run for the full term as well. Aboud and another Democrat — state Rep. Matt Heinz — said they would stay in the race.

"I'm supporting Ron to replace Gabby for the rest of the term," Aboud told The Hill in early March. "But I'm moving forward, and I am focused on the new district in the fall."

Democrats faced what would have been an uncomfortable situation if Barber were to win in the special and then face primary opposition in the regular election months later. As a newly anointed incumbent with the full blessing of Giffords, the state’s most popular Democratic politician, Barber would also have huge advantages that would be almost impossible for the other Democrats to overcome.

Faced with those prospects, Aboud changed her mind and said Friday she was backing Barber.

“He’ll be a good leader for Arizona and I’ll be proud to call him my congressman,” she said. “I hope all Democrats and indeed all Arizonans will join me in supporting him.”

Another Democrat has already dropped out: state Rep. Steve Farley, whose campaign was being run by another former Giffords aide. Aboud’s decision leaves two Democrats ostensibly still in the primary for the full term: Heinz and Nomiki Konst, a college student who had declared a run for the seat but has not made her plans clear since Barber announced his intentions to seek the full term.

Aboud, the state Senate’s minority whip, has another connection to Giffords — she was appointed to replace Giffords in the state Senate in 2006 when Giffords resigned to run for the U.S. House. Aboud was later elected to the seat in her own right.