ISTANBUL - Turkish politicians made their last campaign rounds on Saturday on the eve of an election that is expected to see Prime Minister Tayyip Erdogan win a third term and could give him a mandate to rewrite the constitution.Polling stations were due to open at 7.00 a.m. (0400 GMT) on Sunday in the east, and an hour later in the west. Turnout was expected to be high as is typical in Turkey and irregularities or violence were not expected to be concerns on polling day.