Vernon was one of the principal members of the Congressional Union for Women Suffrage (CUWS) alongside Olympia Brown, Inez Milholland, Crystal Eastman, Lucy Burns, and Alice Paul, and helped to organize the Silent Sentinels protests that involved daily picketing of Woodrow Wilson's White House.

Vernon joined Lucy Burns and Paul as part of NAWSA's Congressional Committee to organize the Woman Suffrage Parade of 1913 that was to occur the following March where it would coincide with the inauguration of Woodrow Wilson.

[3] In 1914, Vernon organized for the Congressional Union, travelling through the Southwestern United States and making her way north through California before arriving in Nevada.

After Martin got into a debate with Senator Key Pittman, Anna Howard Shaw wrote her an angry letter accusing her of being duped by Vernon and the CU.

[9] According to the Women's Heritage Museum's Newsletter, "The petition demonstrated the spirit, will, and ability of Western women voters to elect or defeat members of a political party," [9] One of the first stops of the petition tour was Salt Lake City where Vernon, with the help of Elsie Lancaster, another NWP member, laid the groundwork for Alice Paul to organize a Congressional Union branch in Utah.

[10] At a June 1916 convention in Chicago, women from states that had granted them the right to vote gathered to form the National Woman's Party.

[13] Their strategy ensured consistent press coverage and the eighteen-month campaign saw thousands of women participate and culminated in the arrests of many picketers and the "Night of Terror".

Doris Stevens, in her memoir Jailed for Freedom, wrote that the President was moved when Mabel Vernon said "If the right of those who submit to authority to have a voice in their own government is so sacred a cause to foreign people as to constitute the reason for our entering the international war in its defense, will you not, Mr. President, give immediate aid to the measure before Congress demanding self-government for the women of this country?

Their appearances in the public and political spheres direct addresses to the president, and motivating sacrifice infused the Silent Sentinels militant identity and ultimately contributed to the success of the 19th Amendment.

[24] However, the film does not depict her being arrested and imprisoned: instead, she is shown managing the NWP during Alice Paul's incarceration, including working with lawyers on appeals for the suffragettes.