Turkish voters will decide Sunday whether to replace the Turkish Republic's parliamentary form of government with a strong presidency. It's a vote that could alter — or, opponents say, endanger — the democratic traditions of this key U.S. ally. Turkey is a NATO member helping fight ISIS.
If the referendum passes, it will increase the power of President Recep Tayyip Erdogan. Polls released late in the campaign showed a narrow lead for "yes," with a large number still declaring themselves undecided. Erdogan is predicting at least a 55 percent margin for "yes."