NEW DELHI, Feb. 15 -- The Bharatiya Janata Party (BJP) and the Congress are expected to win most of the vacancies that will arise in the Rajya Sabha in April when the term of 51 members comes to an end in April, although both parties will see their strength diminished marginally.

The Trinamool Congress (TMC) and the YSR Congress Party (YSRCP) are expected to make significant gains in the 245-member House. The change in composition, however, is unlikely to worry the BJP, which still does not have a majority in the upper house (nor does the larger NDA grouping it leads). However, this has not stopped the party from pushing through laws in the Rajya Sabha, thanks to support from parties such as the Biju Janata Dal and the YSRCP.

The BJP, whi...