James Alfred Nash was born in Foxton on 27 July 1871, the seventh of eleven children of Ann Ellen Webster and her husband, Norman Nash, a ropemaker. Norman died in 1880, and three years later Ellen Nash moved to Palmerston North with the family. At the age of 13 Jimmy, as he was known, went to work in the Ready Money Store for five shillings a week. He later became manager and eventually bought the business, opening branches in Bunnythorpe and Levin, and a second shop in Palmerston North's Coleman Place. On 14 February 1895 Nash married Elizabeth Lily Grater (née Keogh) at St Andrew's Church, Palmerston North; they were to have two sons. In 1907 he sold his shops and became a valuer, estate and insurance agent with D. J. Lovelock, a partnership which was to last over 40 years.
That same year, Nash was elected to the Palmerston North Borough Council, beginning his long career in local and national politics. In 1908 he was elected mayor, a position he was to hold until 1923. During this period The Square was redeveloped, the Esplanade and the Cherry Tree Walk were completed, and numerous additions were made to the town's sports grounds. He was a popular figure who enjoyed talking to people as he walked about his borough. During difficult meetings he would often relieve the tension by asking members to join him in a song. Nash strongly supported civic activity and on his retirement from the mayoralty he was unconcerned that the borough's debt had increased six-fold during his time in office. As he said, he had always been supported by a 'strong band of civic minded councillors'.
As chairman of the Palmerston North patriotic committee during the First World War, Nash used his influence as mayor to organise comforts for soldiers and assistance for their families. He was on the committee that set up an emergency camp at Rangiotu when an epidemic broke out at Trentham Military Camp in 1915. In 1918 he was the council's representative on the emergency committee established during the influenza epidemic. Palmerston North was one of the first large boroughs to take control of public buildings and make arrangements for the care of the sick. For her work as head of the Mayoress's Patriotic Committee during the war, Elizabeth Nash was made an MBE in 1919.
Jimmy Nash held numerous other influential positions in Palmerston North. He was a founding member of the local chamber of commerce and garrison band, and was later made a life member of both organisations. He was a member of the Terrace End School Committee for over 20 years, and served for 36 years on the board of governors of the Palmerston North High and Technical Schools. During this time he vigorously promoted better conditions for teachers and improved facilities for schoolchildren.
A founding member (1921) and chairman (1922–32) of the Manawatu–Oroua Electric Power Board, Nash was president of the Electric Power Boards and Supply Authorities' Association of New Zealand for 28 years, and led the struggle for local control of the electric supply industry. He was also a member of the Palmerston North Hospital Board for 41 years, including 12 as chairman. In retirement he continued to promote improved conditions for nurses, and he was chairman of the district nursing committee for more than 20 years.
Nash also made his mark in national politics. He contested the Palmerston seat as an independent Reform candidate in 1914, but came third. In November 1918 the sitting member, David Buick, died, and at the resulting by-election Nash, now standing as the official Reform candidate, won convincingly. His party colleagues, however, were surprised by the content of his maiden speech in September 1919: he strongly supported nationalisation of the mines, railways and inter-island ferries; he promoted superannuation and a decent living wage for all workers; and he was a strong advocate of increased spending on education. A widow's son, Nash remembered his family's struggles and recognised the need for community support for families in times of difficulty.
Nash was a popular local member. In 1922, at his third election, he increased his majority even though the Reform Party's national vote declined. He served as chairman of the Public Accounts Committee (1923–27), junior whip for the Reform Party (1928–31) and the Coalition government (1933–35), and as chairman of committees (1935). At that year's election, however, he finished third behind the New Zealand Labour Party candidate, Joe Hodgens, and the city's mayor, A. E. Mansford. Nash stood again for the New Zealand National Party in 1938, but was well beaten by Hodgens.
In his younger days Jimmy Nash had been a keen sportsman. He was secretary–treasurer of the Palmerston North Bowling Club from 1897 to 1909, president from 1910 to 1912, and was made a life member in 1939. In 1916 he was skip of the four that won the club's first national title and he continued to play competitively at a high level until well into his 60s. A prominent Freemason, he was inducted into Lodge Kilwinning, Manawatu, in 1898 and remained an active member all his life; in 1946 he was appointed past grand master.
Elizabeth Nash, who died in 1942, had always been a strong supporter of her husband's political activities, and their home was remembered as a centre for family gatherings which Jimmy greatly enjoyed. His brother Norman was editor and owner of the Manawatu Evening Standard for many years. In 1951 Jimmy Nash was made a CBE for his services to municipal and national government. At the age of 80 he wrote, 'if you want to enjoy your old age, work on'. He followed his own advice, and enjoyed good health until shortly before his death, at his Palmerston North home, on 24 July 1952; he was survived by his sons. A large crowd of mourners attended his funeral service at St Andrew's Church.