have sought to benefit from conflict.
The BJP has often been accused of fomenting Hindu-Muslim violence. It supports the Bodos' claims and accuses Congress of allowing illegal immigration for electoral gains.
"The Congress Party ... does not have to import illegal immigrants to increase its votebank," Arun Jaitley, a senior BJP leader told parliament. "The government must stop this illegal immigration, the entire border must be fenced, the detection and deportation (of illegal migrants) must begin forthwith."
Congress says most Muslims in Assam are Indian citizens.
In Assam's squalid displacement camps, hundreds of thousands of Bodos and Muslims languish, too fearful to return home after seeing their villages razed, possessions looted or neighbors shot or hacked to death.
Weeks after clashes broke out, convoys of paramilitary trucks still drive through the main roads in this lush rice-growing region. A night curfew remains in place.
Fathoming what happened in Assam is critical for India, whose history is scarred with episodes of slaughter by citizens divided by ethnicity and religion.
Centuries of rule by medieval Muslim invaders drove a wedge between Hindus and Muslims, a suspicion that has only grown since the bloody birth of Pakistan, which was carved from Muslim-majority areas of India in 1947.
Up to one million people were killed in Hindu-Muslim violence when Pakistan was created, which many Indians still refer to as "Partition".
About 170 million Muslims live in India. Many are disenchanted, their alienation partly fueled by the demolition of the 16th-century Babri mosque by Hindu zealots in 1992 and communal riots in Gujarat state in 2002, when around 2,500 people, mostly Muslims, were hacked and burnt to death.
The BJP rose to prominence in the early 1990s on the back of a Hindu revivalist movement. Its leaders led the demolition of the Babri Mosque.
"The BJP is known to play up the communal issue on a much larger scale than Congress. They have an upper caste Hindu agenda," said Asghar Ali Engineer, chairman of the Centre for Study of Society and Secularism.
This has not automatically translated into Muslim support for Congress, which had enjoyed the Muslim vote in the years after independence from Britain.
Congress has often been accused of failing to protect Muslims, and a substantial portion of that vote has waned, going to new regional parties instead.
The Gujarat riots, however, saw the tide turn again in favor of Congress in the 2004 elections, as Muslims saw the party as the only one capable of stopping the BJP and its "Hindutva" or Hindu nationalist agenda.
Making up about 14 percent of India's 1.2 billion people, Muslims are the biggest minority group. Their vote is critical in key swing states such as Assam, Uttar Pradesh and Bihar in the north, West Bengal in the east and Kerala in the south.
With a large chunk of middle class moderate Hindus put off by the Gujarat riots, the BJP has tried to reinvent itself - balancing the need for a softer Hindutva plank with a broader agenda of development and good governance.
Its leaders such as Narendra Modi, chief minister of Gujarat, under whose watch the 2002 riots took place, have in recent years adopted a softer line as they jostle to become the party's prime ministerial candidate in the 2014 elections.
Just how the Assam violence is dealt with could be a deciding factor in votes in certain states.
"Incidents such as what we have witnessed in Assam are read very keenly by the Indian voter. He watches how things are managed or, in this case, mismanaged and exploited," said M.J. Akbar, editorial director of India Today magazine.
There is likely to be a return to anti-Muslim rhetoric and issues such as illegal migration as right-wing parties struggle to form vote-winning policies with an electorate fed up with an opposition that is seen as keener to bash the government than work with it as the economy slows sharply.
For Congress, the issue will be much more complicated, analysts said.
The party will have to consolidate Muslim votes won in the last elections in 2009, while at the same time reassure moderate Hindus who have been angered by the handling of the Assam violence.
"The way this violence took place, the killings and the massive displacement as well as the exodus of northeast people, is likely to lead to more polarization between Hindu and Muslims," said Sabyasachi Basu Ray Chaudhury, political scientist at Kolkata's Rabindra Bharati University.
On Friday, Prime Minister Manmohan Singh told migrants from the northeast they were safe, while adding that India's "communal harmony" was at stake.
Many from the northeast say they need more than just words of reassurance.
Two trains from Bangalore packed with around 4,000 people arrived in Guwahati, Assam's main city, over the weekend.
"I have left due to fear. My job is important, but my life and that of my family is more precious," said security guard Binod Boro, 30, who got down from a train onto an overcrowded platform, followed by his wife and their two-year-old daughter.
(Additional reporting by Biswajyoti Das in GUWAHATI; Editing by John Chalmers and Dean Yates)