Katz ran for the 4th district of the Delaware Senate in 2008.[2] The Republican incumbent, Senate Minority Leader Charlie Copeland, was not seeking re-election, instead running for lieutenant governor.[4] The 4th district is historically competitive, due in part to its high amount of third-party and independent voters.[5] At the time, Republicans had a voter registration advantage in the district.[6] Katz campaigned on a platform of improving public schools and increasing access to healthcare.[4] Katz won the Democratic nomination over nonprofit executive Dee Durham with 63.0% of the vote before edging out Republican State Committee of Delaware member John Clatworthy in the general election by just 1.3%.[2] Katz raised $97,039 for his campaign.[7]
While in office, Katz supported the movement to preserve the historic Murphy House;[8] however, the house was demolished in 2012.[9] Katz also introduced several bills aimed at increasing transparency requirements for lobbyists, though none of them passed committee.[10] In 2011, Katz accused Democratic state representative Bryon Short of plagiarizing a bill he wrote to establish an accreditation process for abortion clinics. Katz also refused to list Short as a cosponsor on his bill due to what he perceived as Short's "poor treatment of the medical community during his private and public deliberations" on an earlier bill. Short acknowledged his bill was very similar to Katz's bill, but argued that both bills were based on language written by the Delaware Department of Health and Social Services and the Medical Society of Delaware months earlier. Short also believed that Katz's bill contained too many protections for doctors, saying "each piece of legislation Sen. Katz introduced has skewed in favor of his profession." Katz asked House Majority Leader Pete Schwartzkopf to open an ethics investigation into Short, but Schwartzkopf refused, pointing out that only members of the House could make such a request. Schwartzkopf also commented that Katz "doesn’t think anyone should propose legislation involving doctors except for him."[11] However, in 2012, Katz and Short collaborated on a bill to strengthen restrictions on door-to-door salesmen that successfully passed the legislature.[12]
Katz ran for re-election in 2012 and was unopposed in the Democratic primary. In the general election, he faced Republican Gregory Lavelle, the Minority Leader of the Delaware House of Representatives. Lavelle had chosen to run for state senate after he and 4 other Republican state representatives were placed in the same district as a result of the 2010 redistricting cycle.[13] Lavelle defeated Katz by a margin of 3.3%.[2] The race was one of the most expensive of the 2012 Delaware Senate elections,[14] with Katz raising $245,128 for his campaign.[7]
Katz returned to politics in 2023 when he accepted the Independent Party of Delaware's nomination for U.S. Senate at its July 1, 2023 convention in Dover, serving as state party chair from 2023 to 2026, succeeded by Ben Woratyla.[3]
Katz accepted the Republican State Committee of Delaware's nomination for the U.S. Senate at its April 25, 2026 convention in Dover.[15][16]