In a blow to the ruling Congress in Himachal Pradesh, former Congress leader Arun Mehra Tuesday joined the Bharatiya Janata Party (BJP).Mehra joined the BJP with hundreds of supporters in the presence of veteran BJP leader and former chief minister Shanta Kumar at an event in Kangra district, some 250 km from here.Mehra lost narrowly to Transport Minister G.S. Bali in the 2012 assembly elections when he contested as an independent candidate.Congress sources said since the party took power in the state, Bali had blocked Mehra's entry into the Congress, making him feel isolated.Mehra belongs to Other Backward Classes (OBC), which is considered the vote bank of the Congress.In a jolt to the Himachal Lokhit Party (HLP), an outfit of BJP rebels, former BJP legislator and HLP leader Naveen Dhiman also joined the BJP.The hill state will vote May 7.