[1] In 2018, Gaughran was elected to the New York State Senate from the 5th district, defeating the long-time Republican incumbent, Carl Marcellino.

[8] Gaughran first ran for the New York State Senate from the 5th district in 1992; his opponent in the general election was the long-time Republican incumbent, Ralph J.

Thus, the district includes all or parts of the hamlets of Glen Cove, Syosset, Jericho, Northport, Commack, Dix Hills, Melville, and Plainview.

[9] In December 1991, Marino, who was the senate majority leader at the time, became known for his "budget-wrangling" which led to the infamous "Hamlet on the Hudson" incident, in which Gov.

[10] Although he had been perceived as a frontrunner for the 1992 Democratic presidential nomination, Cuomo declined to run for president, saying that he was "willing" but not "able" to campaign due to the unresolved state budget crisis.

[10] The 1992 campaign was extremely bitter, with Marino accusing Gaughran of improperly conspiring with a fiscally conservative group called Pack-Up (an acronym for "Political Action Committee to Kick out Unproductive Politicians"), and Gaughran accusing Marino of using state funds to finance the distribution of his campaign mailings.

[14] Marcellino had won the special election on March 14, 1995, to replace Marino, and had been reelected to ten full two-year terms, remaining in office since then.

[19] An analysis conducted by Politico found that, before 2018, the last Democratic candidate to win a state senate election on Long Island in a midterm year was Carol Berman in 1982; Berman defeated Dean Skelos to win a third term before losing to Skelos in a rematch in 1984.

[20] Gaughran was endorsed by The New York Times,[21] Newsday,[22] and numerous local labor unions and activist groups.

[29] A bail reform law passed in 2019 became a major campaign issue for Gaughran and other Long Island Democrats facing a difficult reelection.

[34][35] The police unions, alongside separate independent expenditure groups including Safe Together New York (which received $1.7 million from businessman Ronald Lauder)[32][34] and the Long Island Law Enforcement Foundation,[35] spent millions of dollars in advertisements targeting Democratic state senators including Gaughran.

[31] Gaughran responded with ads featuring him speaking directly to the camera: "If the attacks they are throwing at me seem crazy, well, that's because they are".

[37] Assessing Gaughran's performance in his first term, the editorial board praised his successful efforts on the property tax cap and the bail reform law,[38] but criticized his proposed bill to resolve local tax negotiations with the Long Island Power Authority (LIPA), calling it "unworkable".

[44] Gaughran's victory in a competitive district helped the Democratic Party win a two-thirds supermajority in the state senate in 2020.

No more temporary extensions.... We're beginning to feel the devastating effects of the federal limit on state and local tax deductions....

The Democratic senate majority is going to provide local municipalities and school districts with mandate reform and increase state aid to our region to help lower local tax levies....[49] Gaughran's bill was passed by the senate almost unanimously on January 23, 2019;[50] Gustavo Rivera and Julia Salazar, both Democrats, were the only two votes against Gaughran's bill.

[22][57] Gaughran believes that the New York Secure Ammunition and Firearms Enforcement Act of 2013 should be expanded;[21][57] he favors banning bump stocks and extending the background check waiting period from three to ten days.

[59] Gaughran supports classifying gender identity and expression as "protected classes", meaning that existing state laws prohibiting discrimination would then apply (viz.

[57] In January 2019, each of the 39 members of the Democratic caucus in the state senate, including Gaughran, cosponsored the Gender Expression Non-Discrimination Act (GENDA),[60][61] alongside a conversion therapy ban.

[21][57] In response to his vote in favor of the Reproductive Health Act in 2019, which expanded late term abortion and codified abortion rights statewide, the Huntington chapter of Ancient Order of Hibernians asked Gaughran to resign as a member and barred him from participating in the Saint Patrick's Day parade.

[63] Gaughran favors overhauling the Common Core State Standards Initiative, which New York has formally adopted, saying "this time we need to listen to our teachers, our parents, and our children about what works".

[21][22] He supports appointing an independent re-districting commission to prevent gerrymandering,[22] In 1987, Gaughran married his wife, Carol, who works as a library media specialist.