Does it simply means that he said something during the election campaign? - yes, the second sentence spells that out - He declared that a Palestinian state would never be created on his watch, repudiating his acceptance in 2009 of peace based on two states.
The two state solution refers to the proposition that the only way there will ever be peace between Israel and the Palestinians is for two states to be established side by side, one for the Israelis and one for the Palestinians. Mr Netanyahu previously expressed support for this plan, but then repudiated it during the election campaign.