ALBANY — As state Republican boss Ed Cox’s handpicked gubernatorial candidate slips, Democrat Andrew Cuomo maintains a commanding lead over the GOP field.

A Siena poll released yesterday shows Suffolk County Executive Steve Levy has fallen behind scandalized businessman Carl Paladino in the GOP race. It found Levy would draw 14 percent of the primary vote — down from 15 percent in April.

Meanwhile, Cuomo leads each of the three GOP contenders by 40 or more points.