The government is set to be sworn in on April 2 but could face strong resistance from the far-right Chega party.
Featured Content
Democratic Alliance edged ahead of incumbent Socialists in nail-biting count that saw far-right surge.
Three polls show the right-leaning parties combined, including far-right Chega, could secure an outright majority.
Voters head for the polls in an early election that could see country join a shift to the right across Europe.