WASHINGTON (AP) – Defying a veto threat, the Democratic-controlled Senate narrowly signaled support Tuesday for the withdrawal of U.S. combat troops from Iraq by next March. Republican attempts to scuttle the non-binding timeline failed on a vote of 50-48, largely along party lines. The roll call marked the Senate’s most forceful challenge to date of the administration’s handling of a war that has claimed the lives of more than 3,200 U.S. troops.