Democrats statewide saw a net gain of three seats in the Assembly in the 1995 elections, with two of the pickups coming in the 19th District where Arline Friscia and Wisniewski knocked off the Republican incumbents Stephen A. Mikulak and Ernest L.

On January 27, 2010, Wisniewski was selected to succeed Joseph Cryan as the Chairman of the New Jersey Democratic State Committee.

In 2011, Wisniewski was the Democratic Co-chair of the 2011 New Jersey Apportionment Commission, the group charged with redrawing the lines for the legislative districts following the 2010 census.

[11] Along with State Senator Loretta Weinberg, Wisniewski played a major role in uncovering the Fort Lee lane closure scandal.

[8] In his role as Chairman of the Assembly Transportation Committee, Assemblyman Wisniewski led a fact finding probe into the state's E-ZPass system.

Assemblyman Wisniewski is a prime sponsor of the Motor Vehicle Security and Customer Service Act which was signed into law on January 28, 2003.

[21] He expressed grave skepticism about Christie's claim that he did not know his aides had ordered lanes closed on the George Washington Bridge, and believes that the closures were illegal.

Senator Bernie Sanders announced on January 4, 2016, that Wisniewski would lead his New Jersey operation in his campaign for the democratic nomination in the 2016 United States presidential election.

[2] Wisniewski cited Sanders' efforts to reduce income inequality and take money out of politics as the main reasons for his endorsement.

[21] The contest between Wisniewski and Phil Murphy attracted attention because the two had supported Sanders and Clinton, respectively, in the preceding year's Democratic presidential primaries.

[28] In 2024, Wisniewski reentered government as a commissioner of the New Jersey Turnpike Authority, being named to the seat by Assembly speaker and former running mate Craig Coughlin.