WASHINGTON (AP) — The Constitution says the chief justice is to preside at the impeachment trial of a president. But what about an ex-president? Like so much else about the Constitution, the answer is subject to interpretation. If President Donald Trump’s trial begins after Jan. 20, it’s not clear whether Chief Justice John Roberts would make his way to the Senate chamber as he did last year for Trump’s first trial. Impeachment scholars, law professors and political scientists offer differing views. The choices appear to be Roberts, Kamala Harris, who by then will be vice president, or Sen. Patrick Leahy, D-Vt., who will be the Senate’s president pro tem once the Democrats gain control of the Senate.