What is the derivation of the phrase In Like Flynn?

The phrase “In Like Flynn” is believed to have originated with Ed Flynn.

Flynn was head of New York City’s Democratic party machine from 1922 to 1953.

Flynn’s political machine was always “in” power.

The phrase gained further popularity in 1942, when swashbuckling actor Errol Flynn (1909-1959) was tried and acquitted on charges of the statutory rape of two teenage girls on his yacht.