Carmona, who turns 62 this month, said in a statement that Washington is broken and that it was time "for honest people with real world experience to step forward."
Carmona is the second Democrat to enter the race to succeed retiring Republican Sen. Jon Kyl, joining former state party chairman Don Bivens. Rep. Jeff Flake is one of several Republicans already in the race.
When Kyl first announced his retirement, Democrats listed Rep. Gabrielle Giffords, who was shot in January at a constituent event in Tucson, as a potential candidate. But as she recovers from her injuries, the assumption now is that the three-term Democrat is at most going to seek reelection. She vows in a book due out next week to return to Congress "stronger" than before.
Politico reported that prominent Democrats up to and including President Obama had called Carmona to encourage him to run. Arizona is a seat the party hopes to put into play in 2012 as they defend a narrow 53-47 majority in the Senate.
They are defending 23 seats in their caucus, and initially planned to target six held by Republicans.