Winchester was a member of the Kentucky Senate in 1867 and 1868 when he resigned. He was elected as a Democrat to the Forty-first and Forty-second Congresses (March 4, 1869 – March 3, 1873) but was not a candidate for renomination in 1872. After leaving Congress, he resumed the practice of law in Louisville, Kentucky and was the president of an insurance company from 1875 to 1877. Winchester was president of the Democratic State Convention in 1884. He was also appointed Minister Resident and consul general to Switzerland and served from 1885 to 1889. Building on the experience and observations made during his tenure, he wrote the book "The Swiss Republic", the publication of which coincided with the 600th anniversary of the foundation of the Swiss Confederation.
Winchester died in Louisville, Kentucky, and was buried in Cave Hill Cemetery.