A Democrat, he signed a number of important reforms, including the direct primary and labor laws.

At the New York state election of 1912, Glynn was the running mate of the successful Democratic candidate for Governor, William Sulzer.

Following friction with the dominant Tammany Hall faction, Sulzer was impeached and in August 1913, Glynn was appointed Acting Governor.

After a year in office Glynn was defeated at the 1914 election, by the Republican candidate, Charles S. Whitman.

was published in the October 31, 1919, issue of The American Hebrew; in it he lamented the poor conditions for European Jews after World War I. Glynn referred to these conditions as a potential "holocaust" and asserted that "six million Jewish men and women are starving across the seas".

"[7] He committed suicide by gunshot in 1924, after having suffered throughout his adult life from chronic back pain caused by a spinal injury.