The Democratic Party holds most public offices. Registered Republicans are a minority in the borough, constituting 9.88% of the electorate as of April 2016. Registered Republicans are more than 20% of the electorate only in the neighborhoods of the Upper East Side and the Financial District as of 2016. Democrats accounted for 68.41% of those registered to vote, while 17.94% of voters were unaffiliated.

No Republican has won the presidential election in Manhattan since 1924, when Calvin Coolidge won a plurality of the New York County vote over Democrat John W. Davis, 41.20%–39.55%. Warren G. Harding was the most recent Republican presidential candidate to win a majority of the Manhattan vote, with 59.22% of the 1920 vote.[citation needed] In the 2004 presidential election, Democrat John Kerry received 82.1% of the vote in Manhattan and Republican George W. Bush received 16.7%. The borough is the most important source of funding for presidential campaigns in the United States; in 2004, it was home to six of the top seven ZIP codes in the nation for political contributions. The top ZIP code, 10021 on the Upper East Side, generated the most money for the United States presidential election for all presidential candidates, including both Kerry and Bush during the 2004 election.

Since New York City's consolidation in 1898, Manhattan has been governed by the New York City Charter, which has provided for a strong mayor–council system since its revision in 1989. The centralized New York City government is responsible for public education, correctional institutions, libraries, public safety, recreational facilities, sanitation, water supply, and welfare services in Manhattan.