Clad in a green salwar suit, Rabri Devi was accompanied by her husband and RJD chief Lalu Prasad in a helicopter from Patna.
Both the leaders took out a road show from the helipad to Chhapra town before reaching the district collectorate to file her documents to the Returning Officer Praveen Kumar.
Rabri Devi was accompanied by her husband Lalu Prasad during filing of papers
Later she told reporters "the main contest in Saran is between RJD and BJP-RSS. It's a fight between secularism and communal forces. We'll win and the margin of victory will be huge."
Criticising BJP Prime Ministerial Candidate Narendra Modi, she said, "What can we expect from a person who did not respect his wife and kept her disowned for 40 years? Our nation and its women will not be secure if he comes to power."
Saran will go to polls on May 7.
Incidentally, the notification for this phase was issued on Saturday itself and Rabri Devi became the first person to file her candidature from this seat.
With 14.9 lakh electors, the contest for Saran is being touted as a battle of prestige for Prasad. He won the seat in 2009 defeating BJP General Secretary Rajiv Pratap Rudy by around 52,000 votes.
As Ms. Prasad cannot contest election for his conviction for five years in a Fodder Scam case, he has handed over the seat to wife Rabri.