LISBON (Reuters) - Portugal's main opposition Socialists have slightly extended their lead over the center-right ruling coalition ahead of an autumn election but would fall short of a parliamentary election, an opinion poll showed on Friday.
The Socialists have criticized the government's austerity program but are a mainstream party and analysts say they would be expected to maintain budget discipline and lower deficits if they return to power.
Portugal, which exited an international bailout program last May after years of painful austerity, has not seen the kind of mass support for a radical anti-bailout party as in Spain or Greece. In Spain the leftwing Podemos leads polls ahead of this year's election and in Greece, the radical Syriza party recently swept to power.
In the survey by Eurosondagem pollsters, the Socialists were on 38.1 percent, up just 0.2 percentage points from a month ago. The party saw a jump in support last September after choosing the popular mayor of Lisbon, Antonio Costa, as its candidate for prime minister in the election, but has since stabilized.
The poll showed the Social Democrats of Prime Minister Pedro Passos Coelho trailing well behind on 26.7 percent after shedding 0.2 points. Their coalition partner, the rightist CDS-PP, fell by a whole percentage point to 6.9 percent.
Portugal's election is expected in September or October.
Some Portuguese analysts do not rule out a centrist coalition between the Socialists and the center-right Social Democrats after the election.
The governing coalition presided over three years of tax hikes and spending cuts under the bailout program. Portugal suffered a deep recession but posted its first full year of growth in 2014.
Friday's poll showed the Left Block, the smallest party represented in parliament, gaining half a point to 4 percent. The relatively new, populist Democratic Republican Party was also up by half a point at 3 percent.
LIVRE, another recently formed party that split from the Left Block, was on 2.2 percent. Altogether, including the Communist-Greens alliance that has 9 percent support, these parties have less than half the support the Socialists have.
Eurosondagem surveyed 1,015 people between Feb 5 and 11. The margin of error was 3.08 percentage points.
(Reporting By Andrei Khalip; Editing by Gareth Jones)