buenos air argentine president mauricio macri favor candidate gain grind former populist leader cristina fernandez closely watch senate race country large province buenos air source party two analysts say macri former education minister esteban bullrich let change coalition appear reverse trend since last month fernandez narrowly beat 0.08 percentage point nonbinding primary vote second-place finish would still guarantee fernandez senate seat number vote get closely watch investors see oct. 22 vote gauge potential stage comeback 2019 presidential election analyst ricardo rouvier finish late poll estimate bullrich lead fernandez percentage point buenos air province home nearly 40 percent argentine voters cristina large number vote stick ceiling say interview fernandez 2007 2015 presidency saw latin america economy cut international capital market several company nationalize fernandez indict corruption last year though dismiss charge politically motivate seat congress would give immunity arrest though trial register growth poll say high-level government source ask identify citizen unity party fernandez found launch candidacy june confirm trend say bullrich small lead advantage half percentage point bullrich tie election say campaign spokesman decline name representative another argentine pollster ask identify firm currently survey private clients say bullrich four percentage point lead fernandez polarize show-down fernandez say macri economic austerity hurt provincial poor bullrich largely leave party moderate candidates fernandez break peronism argentina best-known political movement election former transportation minister florencio randazzo attract vote primary sergio massa presidential candidate 2015 election macri finish distant third behind fernandez seek unify opposition bullrich fernandez monday publish letter facebook ask support vote hope peronist voters accompany proposals randazzo massa join majority say jorge taiana fernandez former foreign minister senate candidate interview citizen unity spokesman say party talk peronist mayors support randazzo try convince back fernandez four switch party high hop three say matter many seat coalition pick october argentines elect one-third senate half low house congress macri still lack majority need negotiate tax reform hop pass second half term macri ally gain grind argentina senate election fernandez