Complex sentence: The third party, The Greens, were ahead in the election night count for the seat of Melbourne, however the result is now in doubt--if The Greens win Melbourne, it will be the first state lower house seat to be held by the party.
Split into simpler sentences: The third party, The Greens, were ahead in the election night count for the seat of Melbourne. If this lead holds, it will be the first state lower house seat to be held by the party.