A group of conservative activists huddled behind closed doors Thursday at a Washington hotel to plot strategy to stop Republican front-runner Donald Trump , including calling for a unity ticket to oppose him and a floor fight at the GOP convention to deny him the nomination. The meeting was led by conservative talk radio host Erick Erickson, a longtime outspoken critic of Mr. Trump . “We believe that the issue of Donald Trump is greater than an issue of party. It is an issue of morals and character that all Americans, not just those of us in the conservative movement,...