ISTANBUL A clear majority of Turks will give their backing in a referendum on Sunday to constitutional reforms proposed by the government, a polling institute said in an eve-of-vote boost for Prime Minister Tayyip Erdogan.
A survey by KONDA institute said the reforms, including controversial changes to the judiciary, would pass with a "yes" vote of 56.8 percent in Sunday's plebiscite, seen as a key gauge of Erdogan's support before a parliamentary election next year.
However, KONDA said 17.6 percent of the electorate were still undecided. Earlier polls this week showed the vote was too close to call, with one predicting a narrow defeat for the reform package and the other suggesting it would pass by the slimmest of margins.
Erdogan says the reforms will bring the constitution, drafted after a 1980 military coup, closer in line with those of the European Union, which Turkey seeks to join.
Among the 26 articles that make up the package are changes in the way senior judges are selected. Opposition parties argue that these will enable the government to exert more influence over the judiciary.
Defeat in the referendum would damage the ruling party's morale ahead of the parliamentary election, due by July 2011.
Turkish markets are unlikely to move significantly if the constitutional changes pass, but could turn bearish if the government loses the plebiscite.
The KONDA poll was conducted on September 4-5 and had a margin of error of plus or minus 2 percent.
(Editing by Mark Trevelyan)