The former president is holding a rally in a Colorado city he falsely claims was overtaken by violent immigrants from Venezuela. The city’s leaders, Republicans and Democrats alike, tried to pre-emptively fact-check him. Mike Coffman, the conservative Republican mayor of Aurora, Colo., had a message for former President Donald J. Trump before the Republican nominee for the White House came on Friday to a city he has repeatedly painted as having been taken over by vicious migrant street thugs.The visit, Mr. Coffman said in a statement to The Times, “is an opportunity to show him and the nation that Aurora...