When nearly 15,000 people gathered in downtown Baltimore over the weekend to watch a championship boxing match, the crowd favorite was not in doubt: Gervonta Davis, a Baltimorean who easily fended off the blows of an out-of-town opponent.

Hours earlier, another fight had broken out, this one beginning on President Trump’s Twitter feed. Again, Baltimore rallied in a big way for a local champion: Representative Elijah E. Cummings, a Democrat and civil rights icon in his 13th term in the House.

Mr. Trump continued his assault on Sunday against Mr. Cummings and his district, which stretches from central Baltimore into the Maryland countryside. Mr. Trump called Mr. Cummings, who is black, a “racist” and shared a video of a recent assault on a civilian employee of the Baltimore Police Department.

In response, Baltimore natives, recent arrivals and celebrities lauded their favorite parts of Charm City, from its glistening Inner Harbor to its world-class research university and medical school, Johns Hopkins. The hashtag #WeAreBaltimore quickly became a top trending term on Twitter.