By Aditya Kalra and Rupam Jain Nair
NEW DELHI (Reuters) - Indian opposition leaders Sonia and Rahul Gandhi will appear in court on Saturday to defend themselves against graft allegations in a case they hope to turn to their advantage by energizing their party faithful against Prime Minister Narendra Modi.
The mother and son are the political heirs of the Nehru-Gandhi dynasty, that ruled India for most of its post-independence history, but suffered a humiliating election defeat last year at the hands of Modi's Bharatiya Janata Party (BJP).
The case was brought by a BJP leader who says the Gandhis misused party funds to acquire properties. The Gandhis deny wrongdoing and would seek bail on Saturday, a senior Congress leader said.
The Congress accuses Modi of pursuing a political vendetta against the family. Party workers said there would be uproar if the court treated the pair harshly, which would back-fire on Modi.
"If the judiciary makes a call to detain them for a day, it will be an across-the-board tsunami, but that tsunami is bound to work in our favour in the upcoming state elections," said a Congress party official.
Modi's top aides have denied any involvement in the case.
The court hearing comes after Modi's defeat in a state election last month raised doubt about his popularity and dimmed chances he would be able to win more states to consolidate power in parliament's upper house, where he lacks a majority.
The legal battle has also soured relations between the BJP and Congress in parliament and has apparently scuppered the chances of them working together to clear legislation for landmark tax reform critical for economic growth.
Two other Congress sources said they believed the Gandhis' court appearance would help turn the public mood against Modi.
"Showing up in court and attempting to play victim, in a highly public way, is a way of rebuilding morale among the rank-and-file," said Milan Vaishnav, a political expert at the Carnegie Endowment for International Peace.
Former prime minister and Sonia's mother-in-law, Indira Gandhi, chose to go to jail in a case brought by her rivals in 1977, using it to win sympathy and launch a comeback.
BJP leader Subramanian Swamy, who has brought the lawsuit, accuses the two of setting up a shell company to illegally gain control of properties worth $300 million. The assets were owned by a firm that published a newspaper founded by Rahul's great grandfather, Jawaharlal Nehru.
Congress workers are gearing up for protests. Sanjay Nirupam, the party's chief in Mumbai, said workers were ready to face arrest on Saturday.
Swamy said he would not be cowed.
"I don't like this mob behaviour, these Congress party demonstrations and all," the 76-year-old told Reuters.
"If they launch massive protests, then I can say they are unfit to live in a civilized society and should be sent to jail."