According to an August 19, 2020, article posted on the American Friends of the Documentation Center of Austrian Resistance, when "the German Wehrmacht overran France in May 1940," Leichter, his father and his brother "fled Paris;" and "after some weeks in Montauban, they left France with a forged exit certificate, traveled across Spain to Lisbon, and took a Greek steamer to the United States," where "Muriel Gardiner, one of the greatest rescuers of Austrian refugees in the US, helped the two sons gain admission to a boarding school in Connecticut."

Leichter attended New York City's public schools and graduated from Swarthmore College, magna cum laude, in 1952.

For the Assembly, the bill was amended to allow for women to have abortions until their 24th week of pregnancy or at any time to protect the life of the mother.

[5] For his outspoken criticism of how the Legislature operated, and his willingness to take on powerful interests such as New York City's banking and real estate industries, and the leadership of the Democratic and Republican parties, he was often referred to as "the conscience of the Senate".

As ranking Democrat on the Senate Banking Committee, he sought to advance the interests of consumers and to block harmful legislation.

He frequently called attention to hidden bank and credit card charges and other practices that were costly to consumers.

Active in support of affordable housing, Leichter pushed the Legislature to pass the "warranty of habitability" to protect tenants from dangerous and unsanitary conditions.

He was a leading advocate for tenants' rights and a vocal supporter of New York's rent regulations to protect affordable housing.

The Riverbank State Park, which was built at Leichter's urging on top of a waste water treatment plant, stretches for ten blocks along Harlem's shore of the Hudson River.

[12] As a Democrat serving in the minority party his entire legislative career, Leichter described his strategy as "raising issues", which he accomplished through aggressive debate on the Senate floor, extensive research reports, and frequent news conferences in the Senate lobby and on the steps of New York City Hall.

[13] Leichter announced his retirement from the Senate in 1998 at age 67, and was succeeded by Eric Schneiderman, who went on to be elected as New York State Attorney General in 2010.

[12] In 2000 he was nominated by President Bill Clinton as a Director of the Federal Housing Finance Board (FHFB), which was the regulator of the Home Loan Bank System.

He was associated with various law firms, including Wachtell Manheim & Grouf and until his service on the Federal Housing Finance Board with Walter Conston, Alexander & Green (now part of Alston & Bird).