from Enigmas in Astrology, ch. 3
V.P. Singh was the Prime Minister from 2nd December 1989 to 7 November 1990. A Gajakesari Yoga (Jupiter on an angle from the Moon) in his chart was ruined by a Kemadruma Yoga (no planets conjunct or on either side of the Moon. Rahu/Ketu don't apply).
His Jupiter dasha was over very early in life. In Mercury-Venus he became a charismatic leader for a while. He became the Prime Minister of India for one year and landed in a disaster. In Mercury-Jupiter he again got a chance to become the Prime Minister of India but his bad health has been his biggest handicap. The Sun-Saturn opposition in his horoscope made him very controversial after he introduced the reservation policy as India's Prime Minister. That charisma faded away but he is respected as an incorruptible politician still. That is what a vargottama (planet in the same sign in the natal chart and navamsha) and exalted Jupiter without any aspect does.
Natal Chart of V.P. Singh