BJP national president J P Nadda while addressing an election rally at Tingkhong in the Dibrugarh district on Monday accused the Congress of practising "politics of opportunism" and said that Assam will head into days of "darkness" if the opposition party is voted to power. "The Congress' only aim is politics of opportunism. They are with the Muslim League and fighting against the CPI(M) in Kerala, but joined hands with it in West Bengal and Assam," Nadda said. Like a tusker, the Congress has "two teeth" -- one to show off and another to chew, he said. "The Congress says something and always does the opposite... It is dividing the society," the BJP president stated. Repeatedly attacking the Congress, he said the opposition party "means darkness" while the BJP stands for development. "If you need darkness, then go with the Congress. But if you need development, hold the hands of Prime Minister Narendra Modi," J P Nadda said at the rally.