The 41-year-old former prime ministerial adviser, whose family has a long political legacy in India, won a seat for the Green Party in Stockholm.
Ulf Kristersson steps down after his conservative alliance is squeezed out by a razor-thin margin, bucking Europe's right-wing trend.
Preliminary results show the opposition bloc leading by three seats, a setback for the Sweden Democrats after four years of government influence.
Sweden’s centre-left opposition holds a fragile lead in the final hours of a campaign that could reshape the country's political order.
