The admission came out when Modi filed his nomination for the Vadodara electoral seat, according to the Indian Express. The paper reported that the prime ministerial candidate was forced to declare the assets and liabilities of a spouse under the Representation of the Peoples Act 1951. While Modi acknowledged he had a wife (and reported his own income at Rs. 454,095 or approximately $7,552), he was forced to leave the columns declaring his wife's assets and liabilities blank.
To those who've been following Modi's campaign, however, this isn't so much of a shock. Rumors about Modi's marriage have been around for a long time: As far back as 2009, journalists were trying to interview Jashodaben Chimanlal Modi, a retired school teacher who was said to be Modi's wife. Earlier this year, when it became clear that Modi was likely to be India's next leader, Jashodaben gave an interview to the Indian Express where she said explained that she bore no grudge against her husband for keeping her secret, explaining that it was part of his "destiny."
What explains a secret wife? According to Jashodaben's accounting, she and Modi were married when they were 17 and 18 due to an arrangement between their parents. They were a couple for three years before separating, with Modi reportedly going to travel the Himalayas, and never coming back.
What led Modi away, it seems, was the teachings of the Rashtriya Swayamsevak Sangh (RSS), a strict Hindu organization that is reported to require a vow of celibacy. Modi's time with the RSS eventually led to his leadership of India's second largest political party, Bharatiya Janata Party (BJP), and his Hindu nationalism is seen as one key aspect of his popularity, though it's also a key sticking point for his opponents, who accuse him of failing to prevent the 2002 massacre of nearly 2,000 Muslims.
To Modi's critics, however, his refusal to acknowledge his wife of almost 50 years is a sign of his lack of respect for women. According to various media reports, Jashodaben lives in a one bedroom house and reportedly received a government salary of Rs 14,000 ($233) before she retired. She says she has never remarried after her first experience.
"If a man can't take care of his wife, how can he take care of the country?" Congress Party national spokesman Rashid Alvi reportedly said.
Updated 4/11/2014: A reference to Modi's caste has been added for context, and a reference to Modi and his wife living together for three years has been removed as they may not have been cohabiting for the entirety of that time.