[2] Miller has been a member of the New York State Assembly since 2009, when he won a special election[2] held after the resignation of former Assemblyman Anthony Seminerio.

[10][11] Al Baldeo, who claims he was promised the nomination by Congressman Gregory Meeks, State Senators John Sampson and Malcolm Smith, argued that the selection process was undemocratic.

Miller became the subject of a 2019 internal investigation by the Assembly Ethics Committee stemming from a harassment complaint filed by a female staffer.

The committee found evidence of inappropriate and unprofessional conduct, though the review did not "support a finding that Miller engaged in harassment and/or discrimination.

In August 2020, Assembly Speaker Carl Heastie announced that he would formally sanction Miller for these actions, following the committee's recommendation.