New York State Assembly

Díaz was elected to the New York State Assembly at the age of twenty-three, which made him the youngest person elected to the legislative body since Theodore Roosevelt.^[6]

While in the Assembly, Díaz sponsored, co-sponsored and passed legislation addressing health care,^[7] public records access,^[8][9] minimum wage and overtime pay,^[10] environmental protection,^[11][12][13] equitable labor standards,^[14] insurance fraud,^[15] tenants rights,^[16] transparency and disclosure in all environmental impact statements,^[17] pedestrian safety,^[15][18] school bus safety,^[19][20][21] protection from tax preparers,^[22][23][24] Senior Citizens rights,^[25] wider access to the Senior Citizens Rent Increase Exemption (SCRIE) Program,^[26] and the regulation and accountability of gas and electric companies.^{[27][28][29][30][31][32]}

A member of the Assembly Education Committee, Díaz has been outspoken on educational issues. He has addressed the International Democratic Education Conference (IDEC)^[33] and praised the Campaign for Fiscal Equity's (CFE) efforts to protect the constitutional right to a basic education.^[7][34][35] In 2003, when Governor George Pataki sought to cut the State's higher education budget, Díaz was a vocal critic of this plan and, together with other state legislators, was able to restore funding for some of the Governor's proposed cuts.^[36][37]

Díaz has legislated on behalf of Brownfield Cleanup and Green Roof Tax Abatement,^[38][39] worked to restore the Bronx River which runs through the 85th Assembly District, and opposed environmental racism.^{[11][12][13][40]}

In September 2007, he was named one of City Hall's "40 under 40" for being a young influential member of New York City politics.^[41]

Bronx Borough President

On February 18, 2009, U.S. President Barack Obama appointed Bronx Borough president Adolfo Carrión Jr. to the position of Director of the White House Office on Urban Affairs.^[56] When Mayor Michael Bloomberg declared a special election to choose his successor,^[56] Díaz was considered the leading candidate for the position.^[56][57]

The special election was held on April 21, 2009. Díaz defeated the Republican Party candidate Anthony Ribustello with an overwhelming 87% of the vote, to become the 13th borough president of the Bronx.^[58]

On July 1, 2009, Díaz appointed Delores Fernandez to the reconstituted New York City Board of Education. Fernandez is anticipated to be the sole member of the Board who will have a perspective independent of the mayor, Michael Bloomberg.^[59][60] Díaz ended his first summer as borough president by recommending that the New York City Council reject Related Companies' proposal to turn the Kingsbridge Armory into a shopping mall. In an editorial in the New York Daily News, Díaz wrote that he is "fighting to make sure that this development includes 'living wage' jobs that offer health insurance". Related's proposal is still^[when?] going through the city's review process.^[61]

In 2017, Díaz won the Democratic primary for borough president with 86% of the vote.^[62] On the same day, his father won the Democratic primary to return to the City Council from the Senate.^[62]

In January 2020, Díaz announced that he would not seek re-election in 2021.^[63]

New York City mayoral campaign

In 2018, Diaz was the first candidate to file to run in the 2021 New York City mayoral election.^[64] Diaz dropped out in January 2020, saying he wanted to spend more time with his family.^[64]