buenos air argentina rule party candidate senate key province buenos air 4.8 percentage point ahead opposition candidate accord poll consultancy management fit send exclusively reuters friday country mid-term congressional election hold sunday see early indicator electoral power president mauricio macri go 2019 re-election campaign esteban bullrich macri cambiemos let change party forecast win 35.3 percent vote bid senate accord poll buenos air province home third argentina population opponent former president cristina fernandez 30.5 percent voter intentions accord management fit survey 2,000 voters poll margin error 3.3 3.5 percentage point fernandez love many low-income argentines generous social spend macri proponent free-markets cambiemos criticize reduce popular home heat transportation subsidies laud investors say president policies return argentina sustain growth official candidate see ahead buenos air senate race poll