"Heartiest congratulations on a well deserved victory @NitishKumar sahib. Your victory will prove critical for the nation in the days ahead," Omar wrote on social networking site twitter.com.
"It was the BJP, not Nitish, that made this election a referendum on the Modi Govt. They have to live with the results, win or lose," the former Jammu and Kashmir Chief Minister said.
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Omar sarcastically said if BJP would have won, the victory would have belonged to the leader but the blame for the loss would be borne by the party.
"Always remember victory belongs to the leader, defeat to the party. Simple rule of thumb & all parties, bar none, fall back on this," he said.
On trends that initially showed the BJP-led combine ahead of the grand alliance, Omar said, "The BJP needs to get a refund from some news channels for crackers wasted this morning.