During his time at Parkside, Kreuser interned with Kenosha County Executive, John Collins, and, after completing his M.P.A., was hired as a full-time administrative assistant in the county executive's office. Kreuser later credited the experience he received working in the county executive's office, getting to know the county and state government, with enabling his success as a legislator. He was still working for the county executive when, in 1993, a chain of events—starting with the appointment of local-area congressman
Les Aspin to join the cabinet of newly inaugurated President
Bill Clinton—resulted in a vacancy in the
Wisconsin State Assembly district in which Kreuser resided. A special election was called for August 1993, and Kreuser was elected. He topped his two Democratic opponents in the primary, carrying just over 50% of the vote, then defeated his Republican general election opponent, William F. Cantwell, by a wide margin. Kreuser went on to win re-election seven times, receiving attention and praise from his colleagues as an up-and-coming leader in the party. In 2001, amid discontent within the caucus over the results of the 2000 election, Kreuser made a successful bid with Assistant Minority Leader
Spencer Black of Madison, to challenge Krug as floor leader. Black was elevated to Minority Leader and Kreuser was elected as Assistant Minority Leader, in what was seen as a repudiation of the
Democratic Leadership Council in Wisconsin. Black stood down as leader at the end of the
2001-2002 term, and Kreuser was elected just after the 2002 election as the next Minority Leader. Over his three terms as minority leader, Democrats increased from 41 seats in the Assembly to 47. ==County Executive==