He was active in local politics, serving as a charter member of the Lake Pasadena Neighborhood Association and working as State Representative Lars Hafner's campaign manager.

[8] When Kersteen resigned from the City Council to unsuccessfully run for the State House in 2000, Kriseman was appointed to replace him.

Kriseman campaigned on his plans to raise the city's quality of life by promoting economic development and effective law enforcement, and expressed his support for an ordinance to ease regulations for homeowners seeking to add bedrooms to their homes, while Homol campaigned on his support for building desalination plants.

He campaigned on a "progressive" vision for the city, which included support for "pedestrian safe zones, land-banking, live Internet access to council meetings and creative use of swimming pools such as holding "dog paddles" so people can bring their pets to swim," noting that government can be "about creating opportunities for fun, too.

Kriseman, however, emphasized his progressive credentials, noting that he was "socially liberal," and expressed his support for higher teacher pay, smaller classroom sizes, mandatory community service for high school students, and the Save our Homes cap.

[14] Owing to the liberal nature of the district, the contest was not close, and Kriseman won his first term easily, receiving 60% of the vote to Piccolo's 40%.

He opted against seeking re-election in 2012, declaring, "I've been in office for 12 years, the last six in Tallahassee, and it's been extremely challenging and frustrating being up there fighting a system that I think is broken.

Kriseman cited Foster's lack of leadership, the handling of the Tampa Bay Rays' desire to leave Tropicana Field, and issues with the St. Petersburg Pier as reasons for his mayoral run.

[20] The Tampa Bay Times, criticizing Foster's "lack of vision and unsure footing," strongly endorsed Kriseman, citing his "stabilizing influence" on the City Council and his focus on "environmental efforts and public education" in the legislature.

The Times praised the "new energy" that Kriseman would bring to the mayor's office in negotiating with the Rays, redeveloping the Pier, and improving city services.

In December 2015, Kriseman received media attention after he tweeted about "barring" Donald Trump from entering St. Petersburg,[27][28] which he did in response to Trump's earlier controversial comment on banning all Muslims from entering the U.S. in the wake of deadly terrorist attacks in Paris and San Bernardino, California.