* Bundesbank chief Weidmann a tough sell for ECB presidency (Adds Merkel comment): BERLIN/FRANKFURT (Reuters) - Germany’s Jens Weidmann is seeing his prospects of becoming European Central Bank president fade, amid signs that trade issues handled in Brussels are eclipsing Berlin’s concerns about securing its man to steer monetary policy. German business daily Handelsblatt reported on Wednesday that Chancellor Angela Merkel is focusing on winning the European Commission presidency for a German rather than backing Bundesbank chief Weidmann to succeed Mario Draghi.