The kind of opposition unity displayed in Uttar Pradesh's Kairana seat that led to the BJP's defeat in the bypolls is a "serious setback", said senior party leader Chandan Mitra. The BJP's Hukum Singh had won in 2014, netting over 50 per cent of the vote share. But this time there was a four per cent swing away from the party that led to the defeat of his daughter who was pitted against a Rashtriya Lok Dal (RLD) candidate backed by the Samajwadi Party, Bahujan Samaj Party and the Congress. "If the opposition unites, which they hadn't all this while, the BJP has a really serious fight on its hands in the run-up to 2019," Mr Mitra told NDTV.