With three regional parties BJD, TRS and YSRCP holding the key to the election of Rajya Sabha's deputy chairman, both the ruling NDA and the opposition parties are trying to woo them. The opposition's combined strength in the upper house including TDP has 117 votes. But the winning candidate will require 122 votes in the 245-member house. The BJP, which is the single largest party in the Upper House has the support of 106 members, including that of 14 AIADMK members. Sources have also told NewsX that Congress is unlikely to field its candiate for its post of Deputy Chairmen of Rajya Sabha and that the party believes in sending out the message of opposition unity.