I knew eventually more details would come out:
“… In September 2013, more than a year before Cuomo was up for reelection, Tishman Speyer President and Co-CEO Rob Speyer summoned a select group to discuss the 2014 election: State Republican Chairman Ed Cox, Republican Senate Conference Leader Dean Skelos, then–state GOP Executive Director Michael Lawler and Republican Senate Counsel Robert Mujica … The governor had asked him to call this meeting, Speyer explained, because like them, Cuomo wanted to keep the State Senate in Republican hands. If the party ran a candidate who could potentially beat Cuomo in 2014, however, the governor would spend $40 million to defeat that candidate and Senate Republicans. Skelos responded first: The person they were considering was Westchester County Executive Rob Astorino, he said. At this point, Astorino had not yet won re-election in Westchester. “Well, that is the one candidate you can’t run,” said Speyer … After a heated back-and-forth, the meeting ended with no agreement …”
That means the agreement came later after more was put on the table.