From New York City to Los Angeles, many of the nation’s biggest cities have turned even harder to the left under President Donald Trump, putting pressure on local officials to embrace the leading progressive presidential candidates — or withhold their endorsements entirely for fear of antagonizing newly energized activists. It’s a drastic political shift in some places, where for decades entrenched party bosses crushed any signs of life on the left or tended to put the weight of big-city institutional support behind Democratic establishment-oriented candidates.