OPEIU has about 25,000 members in New York, and 145,000 nationwide. It was a big supporter of Green when he ran in, and narrowly lost, the 2001 race for NYC mayor, OPEIU’s Michael Goodwin said.

Democratic AG frontrunner Andrew Cuomo, who has locked up the bulk of big union endorsements in this race so far, was also a contender for the OPEIU nod, Goodwin said. But the executive committee’s vote was not close.

“Mark Green has been working with us for many years, his whole life,” Goodwin said. “The problem with primaries is we’re forced into choices. There were two friends vying for one office, and we had to make a choice.”

(I think it’s safe to assume he meant Green and Cuomo are both friends of the union, and not of each other, given the high level of contention in this race).