As a leader, he was known as a political fixer, and honored loyalty, running a citywide patronage system involving gratuity exchanges that ultimately resulted in multiple municipal corruption scandals.

Following the election of Ed Koch to the mayoralty in 1977 (an outcome facilitated by Esposito's support, which was obscured by mutual agreement due to Koch's political origins in the postwar, Manhattan-based "Reform Democrat" movement), Esposito emerged as New York City's paramount political leader and de facto shadow mayor, with a multiracial sphere of influence that encompassed such disparate figures as Bronx political leaders Stanley M. Friedman, Stanley Simon and Ramon S. Velez; Brooklyn Assemblymen Stanley Fink (who also served as Speaker of the New York State Assembly at the peak of Esposito's influence) and Anthony J. Genovesi; Queens Borough President Donald Manes; Brooklyn Borough President Howard Golden; Brooklyn Representatives Shirley Chisholm, Leo C. Zeferetti and Fred Richmond; conservative fixer Roy Cohn; real estate developers Fred and Donald Trump (the latter would ultimately serve as the 45th President of the United States between 2017 and 2021 and is currently serving as the 47th President of the United States from 2025 until 2029); and American Mafia leaders Anthony Scotto and Paul Vario.

[7][8] In 1983, investigations into his activities mounted; this, along with a thwarted leadership challenge from erstwhile protege Genovesi (who Esposito believed had been "openly salivating" for his departure[9]) would prompt his retirement in January 1984.

[10] As a result of this and related scandals (including Manes' suicide and Friedman's conviction on federal corruption charges) amid the political emergence of reform-minded rivals David Dinkins and Rudy Giuliani, the Esposito machine effectively collapsed.

During this period, several fledgling African American politicians also withdrew their support, precipitating the 1990 election of Clarence Norman Jr. as county chairman of what had momentarily descended into a "largely vestigial structure".

"[15] After dropping out of school, Esposito found employment at an insurance business (a field he would return to throughout his career) operated by Jim Powers, a former United States Marshal and local Democratic leader.

Amid redlining and white flight-driven demographic shifts in Ocean Hill-Brownsville and adjacent East New York throughout the 1950s and 1960s, Esposito's predominantly Italian and Jewish base gradually migrated to southeastern Brooklyn's semi-suburban belt of Canarsie, Flatlands and Mill Basin, culminating in the formation of the gerrymandered 39th Assembly District to represent these constituencies in 1972.

From 1960 to 1970, he also served as assistant vice president of the Kings Lafayette Bank (which was subsumed by the Edmond Safra-led Republic New York in 1966) for an indeterminate period of time "despite no apparent experience" in the profession.

"[17] Although Esposito attained his longtime goal of becoming chairman of the Kings County Democratic Committee in 1969 as part of a byzantine power-sharing agreement with "sometimes friend and often business partner"[18] Stanley Steingut (who sought to consolidate his control of the New York State Assembly's Democratic caucus in preparation for assuming the speakership), the Jefferson Club's influence was initially overshadowed by the enduring dominance of Steingut's East Flatbush-based James Madison Democratic Club, a predominantly Jewish political clearinghouse for such figures as future New York City Mayor Abe Beame, veteran New York State Comptroller Arthur Levitt Sr., prominent jurist Nat Sobel and members of the Trump family.

After Beame lost the mayoralty in 1977, the balance of power in municipal politics gradually shifted to Esposito, with accelerating white flight in East Flatbush and the concomitant death of Steingut organization éminence grise Beadie Markowitz (an Esposito ally for decades because of their mutual roots in the Schorenstein machine) in early 1978[19] all but assuring the then-Speaker's decisive defeat by Andrew Stein-backed primary challenger Murray Weinstein (later succeeded by his daughter, Helene Weinstein).

Some observers have asserted that Esposito's authority was functionally attenuated throughout this period due to the failed campaigns of several Esposito-Steingut endorsees, including former Administrator of the Small Business Administration Howard J. Samuels (who unsuccessfully sought the 1974 Democratic gubernatorial nomination in a voluble campaign managed by Ken Auletta) and longstanding Washington Senator Henry M. Jackson, a seminal neoconservative who ran for the 1976 Democratic presidential nomination; both were primarily favored by Steingut, with the latter retaining support from the machine for most of the 1976 primary season (mainly due to his advocacy for Israel and opposition to desegregation busing) despite late Madison Club attorney James Harrison Cohen's efforts to campaign for Jimmy Carter, the eventual nominee.

The unanticipated election of alleged Mangano-Caracciolo proxy Bernard M. Bloom (then leader of the eastern Flatbush-based Andrew Jackson Democratic Club) as Kings County Surrogate (a role charged with overseeing lucrative probate and estate proceedings) in 1976 may have deprived the Esposito-Steingut machine of a key patronage tranche as retribution for the 1969 "coup",[20] although Cohen asserted in his 2019 memoir that Esposito personally "tapped" Bloom to serve in the role after "quietly [supporting]" Hugh Carey, the Mangano-Caracciolo-Bloom faction's successful 1974 gubernatorial candidate.

[21] In the summer of 1979, Esposito was tried for allegedly violating a state law barring New York county political leaders from engaging in business dealings with race tracks.

In the fall of 1985, during an FBI investigation into the Genovese crime family, Esposito was heard speaking with lifelong friend Federico "Fritzy" Giovanelli, a caporegime in the organization.

[citation needed] While Biaggi was acquitted of both bribery and conspiracy, he was convicted of accepting an illegal gratuity and obstruction of justice, sentenced to two-and-a-half years in prison, and fined $500,000.

[33] Donald Trump, whose family's real estate business frequently interlocked with elements of the Brooklyn Democratic machine, respected Esposito and his management style.

While serving as county leader, Esposito eschewed written memoranda and held important meetings in the basement of his mother's Canarsie house to evade potential wiretaps at his Downtown Brooklyn office and Mill Basin home.