New Delhi, Feb. 11 -- Ritu Tawde, a BJP corporator from Ghatkopar East, will formally assume office as Mumbai's mayor on Tuesday after being elected unopposed in the Brihanmumbai Municipal Corporation, marking a rare political shift in India's richest civic body and ending Shiv Sena's quarter-century hold on the post.

A two-time corporator, Tawde becomes the city's eighth woman mayor and the BJP's first in Mumbai since 1982-83, as the ruling Mahayuti alliance consolidates its position inside the municipal corporation even while the BMC continues to function under an administrator.

Tawde has served as a corporator twice from Ghatkopar East, a key suburban ward that has been politically significant in Mumbai's municipal contests. Her elev...