Former congresswoman Stephanie Herseth Sandlin announced Monday that she will not run for South Dakota's open Senate seat in 2014, sharply increasing the likelihood that  Democrats will lose a seat their party now holds.

"While I know you share my confidence that working together we could win a statewide race next year, I’m also confident that the decision not to run is the right decision for Max, Zachary, me and our entire family," Herseth Sandlin wrote on her Facebook page.