ANKARA, June 12 (Reuters) - Turks began voting in an election on Sunday that is expected to return Prime Minister Tayyip Erdogan to office for a third consecutive term and could give him a mandate to rewrite the constitution. A Muslim democracy and European Union-candidate, Turkey has become an economic powerhouse and influential player on the global stage since Erdogan's AK Party swept to power in 2002. Polling stations in the country of 74 million opened first in the east, including in the restive Kurdish region. There were no immediate reports of trouble. Polls were due to open later in the west, including in the capital Ankara and Istanbul. "I hope these elections will be good for the country," said Mehmet Mikailoglu after casting his vote in Diyarbakir, the largest city in Turkey's economically backward southeast where a decades-old Kurdish separatist conflict is focused. Opinion polls have shown Erdogan set to win four more years of single-party rule in the nation that straddles Europe, the Middle East and Asia. His support has been built on his success in creating a booming economy and in ending decades of chaotic coalitions, military coups and failed international financial bailouts. The only doubt hanging over Sunday's vote was about the margin of victory. Erdogan needs more than a simple majority to be certain of pushing through plans for a new constitution to replace one written in 1982, two years after a military coup. Erdogan, whose party evolved from banned Islamist movements, says the new charter will be based on democratic and pluralistic principles that will bring Turkey closer to EU standards. While foreign investors traditionally have seen AK as the most market-friendly party, Erdogan's critics say he has an authoritarian streak. They fear he will use his growing power to switch to a more presidential system of government, with an eye on becoming president himself in the years ahead. Opponents also point to rampant use of wiretaps by state agencies, the detention of journalists critical of the government, nepotism and a widening gap between rich and poor. CONSTITUTION AK, a socially conservative party, held 331 of the 550 seats in the last parliament. Polls show it scoring the same or more. At least 330 seats would give AK the power to call a referendum on rewriting the constitution. If it gets more than a two-thirds majority, it will be able to change the constitution without resorting to a plebiscite. "These elections are not about who wins, but about whether AK will win a strong majority to rewrite the constitution," Sinan Ulgen, from the Istanbul-based Centre for Economics and Foreign Policy Studies, told Reuters. The opposition has been in disarray since AK routed establishment parties tainted by graft and financial mismanagement in 2002. The Republican People's Party (CHP), the party of Turkey's once-dominant secularist, Westernised elites, has been revitalized under new leader Kemal Kilicdaroglu. Opinion polls put support for the CHP at 25-30 percent. Kilicdaroglu has dropped the CHP's old scaremongering tactics of accusing AK of wanting to turn Turkey into an Iran-style Islamic state and has focused his campaign on human rights and inequality, while warning of Erdogan's growing power. The performance of independents fielded by the pro-Kurdish Peace and Democracy Party (BDP) and far-right Nationalist Movement Party (MHP) could prove key to AK's margin of victory. The outcome of Sunday's vote will have repercussions outside Turkey, a NATO member and U.S. ally that has forged stronger ties with fellow Muslim neighbors. Analysts have warned the new government will face sobering economic challenges. The current account deficit is ballooning, fiscal policy needs tightening to cool overheating and youth unemployment is high in a country where the average age is 28.
