The International Brotherhood of Teamsters may not officially be endorsing a presidential candidate this year, but a scathing analysis concluded that its president has already done Donald Trump “an unreasonably large favor.” Sean O’Brien divided the union, one of America’s largest when he spoke at the Republican National Convention. That divide only deepened after union leadership declined to make a presidential endorsement for the first time in 28 years, with several local units coming forward to make their endorsements for Vice President Kamala Harris. O’Brien’s predecessor James P. Hoffa ev…