NEW YORK. According to reports released Thursday, former Mayor Rudolph Giuliani is backing away from a run for governor, after months of speculation, but is leaving the door open to a challenge of Sen. Kirsten Gillibrand, who has been perceived as vulnerable in polls. A gubernatorial run could have pitted Giuliani against Attorney General Andrew Cuomo, who — even though undeclared — is seen as the leading Democrat contender for the seat.