CPI has blamed Rahul Gandhi's decisions for the loss.
Decisions taken by Rahul Gandhi led to divisions within the opposition, CPI national secretary Atul Kumar Anjaan said Thursday and asserted that the policies of the Congress scion opened the doors for Narendra Modi's victory.
Riding on a massive Modi wave sweeping through most parts of India, the BJP was set to return to power Thursday as it led in 292 seats while the Congress trailed far behind with 50, according to trends released by the Election Commission for all 542 seats that went to polls.
"The BJP fought these elections on the basis of social and religious divisive policies and the agenda was set by them on this basis.
"But more significant is the fact that the unity of the opposition has been damaged by the Congress. The policies and decisions of Rahul Gandhi has weakened opposition unity, led to divisions and opened the doors for Modi's victory," the Communist Party of India national secretary said.
The party's other National Secretary, D Raja told PTI that although now was not the time to blame any individual party or leader for the dismal performance of the Opposition, it is also true that it was because of the unity among the allies that in states like Tamil Nadu, the BJP wave did not have any effect.
"Every political party should introspect and analyse how this situation happened. We have to rework strategies, reorganise party and reconnect with the people.
"With BJP capturing power, they will now aggressively pursue Hindutva agenda and cultural nationalism. The secular democratic parties have failed to form a credible alliance and that has been our failure," Raja said.
If the trends stay until final results, the BJP would have improved on its 2014 performance when it had won 282 seats on its own in the 543-member Lok Sabha. Adding the seats won by its allies, the BJP-led National Democratic Alliance could win 343 seats, up from 336 in 2014.
"I think it looks like nationalism worked for them in northern states and Karnataka," CPI general secretary Suravaram Sudhakar Reddy told PTI.
"Nationalism worked (for the BJP)... points raised by opposition unemployment, price rise, and omissions and commissions of the BJP did not stand before nationalism, particularly in northern states," he said.
Reddy said lack of electoral understanding between the Left parties and the Congress helped the BJP make big gains in West Bengal.
"There was polarisation between Trinamool and the BJP, as there was no understanding between the Congress and the Left. The 'friends' behind the Left who wanted to defeat the Trinamool went towards the BJP", he said.
Asked if he thought the Left and the Congress should have fought the elections together in West Bengal, he said: "Yes, there would have been some confidence in the ranks".
"Sabarimala undercurrent" helped the UDF electorally in Kerala, where Rahul Gandhi contesting from Wayanad also consolidated the minority votes behind the Congress, he added.
