Sen. Ruth Hassell-Thompson (D-Mount Vernon) is stepping down in July to accept a position in the Cuomo administration.

Her departure apparently will leave the State Senate with 31 Democrats and 31 Republicans and one vacancy, though the GOP will retain control thanks to six breakaway Democrats.

advertisement | advertise on newsday

Hassell-Thompson will be appointed special adviser in the state Division of Homes and Community Renewal, Gov. Andrew M. Cuomo announced Friday.

She has served in the Senate since 2001 but had looked to move on previously. She ran unsuccessfully for mayor of Mount Vernon last year. Her Mount Vernon-Bronx district is overwhelmingly Democratic.

Democrats seem poised to take a numerical majority in the Senate if Assemb. Todd Kaminsky’s (D-Long Beach) withstands an absentee ballot count in Tuesday’s special election to replace ex-Sen. Dean Skelos. Republican backers of Chris McGrath have said they expect to lose. If so, that would make it 32 Democrats and 31 Republicans until Hassell-Thompson departs.

But Senate Majority Leader John Flanagan (R-East Northport) is all but assured of maintaining control through the 2016 legislative session after forming a governing coalition that includes six renegade Democrats.