Joseph Lhota is officially out as Metropolitan Transportation Authority Chairman.
His resignation as head of the mass transit agency took effect Tuesday.
Lhota was hailed for getting the transit system up and running after Hurricane Sandy.
He announced last month he would step down to explore a run for City Hall.
The Republican served as a deputy under former Mayor Rudolph Giuliani.
MTA Board Vice Chairman and former Bronx Borough President Fernando Ferrer will serve as acting chairman until Governor Cuomo appoints a successor.