The three-page memo, marked confidential and obtained by The Associated Press on Tuesday, indicates the party was "mere minutes away" from giving its nomination for governor to Fordham University Law professor Zephyr Teachout before it gave the nomination to Cuomo at its convention on Saturday.
"In the past few days, the decision has seen critics from a number of corners," the memo reads, before going on to rebut claims that the party was wrong to endorse Cuomo or has no way to ensure he lives up to his promises.
The Working Families Party is a coalition of unions and progressives and has emerged as a leading liberal voice in New York, helping to elect Democratic New York City Mayor Bill de Blasio. Some party members have questioned Cuomo's liberal credentials and criticized his business-friendly tax policies.
Polls show Cuomo's substantial lead over Republican Rob Astorino would be cut in half if he were also to face a Working Families candidate in the fall election.