Joanne Maglione, 42, a lawyer at Jaspan Schlesinger in Garden City, received the nod at a Democratic executive board meeting Tuesday night.
Republican Gary Slavin, a past president of the Massapequa Chamber of Commerce, has publicly expressed interest in running for the seat.
Maglione, a first-time candidate, will run on the Democratic line. She describes herself as an "independent Republican," and said that if elected, she will decide on an issue-by-issue basis whether to caucus with the Democrats or the GOP. The legislature is now split between 9-9 between Republicans and Democrats.
"I can be a nice check and balance on the Republican Party to make sure they do what they are supposed to do," she said.
Maglione, who practices law under her maiden name, Joanne Oweis, is a lifelong Republican who served as a Nassau deputy county attorney from 2003 to 2008.
A married mother of two boys, Maglione said she was inspired to run for office after receiving notice last week that her school tax bill will rise by several hundred dollars in 2013.
"I am going to speak up for people in the community," she said. "Republicans promised our taxes would not go up, but they did."
Maglione was granted a Wilson-Pakula authorization allowing her to run as a Democratic candidate.
Santino declined to comment.