The move leaves a clear path for former U.S. Surgeon General Richard Carmona to win the Democratic primary, The Washington Post reported. Most of the Democratic Party had already lined up behind Carmona to fill the seat that will be left vacant by the retirement of Republican Sen. Jon Kyl.
"The continuing head-to-head competition of our Democratic primary is draining resources that we will need as a party to win the U.S. Senate race in November," Bivens said in a statement Wednesday. "While I am confident we would win this primary, the cost and impact on the party I've spent my life fighting for could diminish our chance to achieve the ultimate goal: winning in November."
U.S. Rep. Jeff Flake and businessman Wil Cardon are vying for the Republican nomination.
Celebrity Breakups and divorces of 2014 [PHOTOS]