Top Congress and BJP leaders will launch a blitzkreig in Karnataka from Friday seeking to give a big thrust to the chances their parties in the April 17 Lok Sabha polls that holds out the prospect of a tight race between the two principal players. br br Even as the real political fever would be kick-started 10 days before the actual voting date, Congress and BJP leaders Sonia Gandhi, Rahul Gandhi and Narendra Modi will visit the state to pump its volunteers.