THIRUVANANTHAPURAM: Opposition leader VD Satheesan on Friday alleged that the arrest of KPCC president K Sudhakaran is part of a political conspiracy. "This is a black day in the democratic history of Kerala. The Congress and the UDF will strongly oppose the move to file false cases against the leaders who are constantly criticizing the government and making allegations of corruption. Don't think that the opposition can be silenced by threats and false cases," he added.