The 93-year old 11-time legislator and a former minister, is still fit, but has opted out on health grounds from the rough and tumble of campaigning and field politics.
He had made the announcement of his plans last year, but recently the PWP General Secretary Jayant Patil officially declared Deshmukh's decision though he said the party was keen he should contest.
Deshmukh, who represented the Sangole seat in Solapur district of western Maharashtra holds the record of the second-longest serving law-maker after the late DMK supremo M. Karunanidhi.
Against Deshmukh's 56 years in the legislature, Karunanidhi was a Tamil Nadu Legislative Assembly for a staggering 61 years as MLA elected 13 times.
The highly-respected Deshmukh, influenced by the Leftist ideology since his student days and started his legislative career way back in 1962 when many of the modern-era politic were not born or not in politics.
Since then, he has won every election barring 1972 and 1995, served as minister twice under the then Chief Minister Sharad Pawar-led Progresssive Democratic Front in 1978, and later when the PWP allied with the Congress-Nationalist Congress Party in 1999 under the late Chief Minister Vilasrao Deshmukh.
Though conscious of Deshmukh's towering presence in the party and state politics, the PWP has come to terms with his departure and decided to nominate industrialist Bhausaheb Rupnar.
However, following a massive uproar which alarmed party circles, the PWP backtracked and passed on the mantle to Deshmukh's grandson, Aniket Deshmukh, a doctor.
Miffed by the last minute change last weekend, Rupnar walked over to the Shiv Sena and is likely to work for former legislator and Ganpatro Deshmukh's traditional political rival, the Sena candidate Shahajibapu Patil.
With these developments, while one old-world era in the form of Ganpatrao Deshmukh officially ends, another family aeon in the form of his grandson Aniket Deshmukh will take wings.
The Oct. 21 elections outcome will decide whether the gambit of the PWP a partner of the Opposition alliance has paid off.
( With inputs from IANS )