Former Arizona Democratic Party Chairman Don Bivens formally announced his Senate campaign this morning in a video posted to his campaign website.
"I'm not a politician. I've spent my entire career in the private sector working with business large and small," Bivens, a partner at Snell & Wilmer, said in the video. "I'm running for the United States Senate because we can't keep sending the same folks back to Washington and expect a different result."
Bivens is the first Democrat to officially enter the race, which Roll Call Politics rates as a Tossup.
Giffords was a likely Senate candidate until she was shot in the head in January, and she's expected to run for re-election if she seeks any office next year.
Rep. Jeff Flake is the frontrunner for the Republican nomination, though he'll have some competition from wealthy business investor Wil Cardon and a couple of others.
GOP Sen. Jon Kyl's retirement made Arizona one of only a handful of possible pickup opportunities for Democrats, including Nevada and Massachusetts, in a year when the party is defending more than twice as many seats as Republicans. The GOP must win four seats to reclaim the Senate majority.
Former Sen. Scott Brown, R-Mass., candidate for U.S. Senate in New Hampshire, holds his hand over his heart during the singing of the national anthem as he waits to take the stage for his town hall campaign rally with Sen. John McCain at the Pinkerton Academy in Derry, N.H., on Monday, Aug. 18, 2014.