At break point, a look at what Nitish Kumar has against Narendra Modi

When the Gujarat riots of 2002 took place and hundreds of Muslims were killed, Nitish Kumar was the country's Railways Minister. The BJP-led coalition, the NDA was in power. Nitish's party, the Janata Dal United or JDU is a part of that coalition. Its leaders claim that Nitish told the BJP that Mr Modi had not acted soon or strongly enough.

Nitish Kumar, JDU sources allege, was persuaded to stay with the NDA by then Defense Minister George Fernandes who argued that the alliance was making progress in Bihar in dislodging Lalu Yadav and his wife, Rabri Devi, from power. Nitish's critics like CP Thakur of the Bihar BJP say he chose to stay with the alliance because he benefitted from it, and attacks Modi now because despite his denials, he aspires to be Prime Minister.

The national election in 2004 was punishing for Nitish Kumar. Of the 40 Lok Sabha seats, the JDU-BJP alliance won just 11. Nitish Kumar contested the election from two constituencies- Barh and Nalanda. He lost Barh, a seat he had won five times.

The electoral verdict shaped his strategy. He decided that Muslims in Bihar -15% of the population - were punishing the BJP-JDU alliance in retaliation for the Gujarat riots. His detractors emphasise that his stand against Narendra Modi is driven by electoral math.

The next year, in 2005, Nitish banned Narendra Modi from campaigning in Bihar for the state election.

The BJP-JDU partnership swept the Bihar election, and convinced Nitish Kumar and his party that their anti-Modi stand is politically profitable.

In the national election in 2009, the JDU told the BJP that Narendra Modi could not campaign in Bihar.

Nitish Kumar and Narendra Modi shared the stage at a rally in Ludhiana to campaign for the National Democratic Alliance, or NDA. The coalition is anchored by the BJP; the JDU is a senior member. Narendra Modi caught Nitish off-guard by hugging him on stage. Sources close to Nitish say that he was privately furious, and relieved that by then, voting in Bihar had ended.

A year later, Narendra Modi arrived in Patna to attend a meeting of the BJP's national executive. In local newspapers, the some NGO from Gujarat ran ads that showed Modi and Nitish sharing the stage in Ludhiana. The ad highlighted that the Gujarat government had sent five crores to assist Bihar in 2008 when the state was deluged with floods. Nitish Kumar returned the money and cancelled a dinner he was meant to host for BJP leaders.

Nitish is regularly irked by the fact that Narendra Modi gives "state guest" status to Raj Thackeray, the politician from Maharashtra, when he is in Gujarat. Mr Thackeray frequently attacks Bihari migrants for taking away jobs in Mumbai from locals.