MILWAUKEE — Senator Elizabeth Warren accused President Trump of stirring “hate.” Julián Castro said the president had acted “like a dictator.” The Trump administration’s actions, warned Beto O’Rourke, threaten to “stain” the nation’s conscience.

The Democratic presidential candidates, gathered here in Milwaukee on Thursday to address Latino voters, excoriated Mr. Trump’s immigration and deportation policies and channeled rising anxiety among a constituency that could be crucial in the 2020 primary race.

The appearances by Ms. Warren, Mr. Castro and Mr. O’Rourke, as well as by Senator Bernie Sanders of Vermont and Representative Tulsi Gabbard of Hawaii, were part of a multiday event, hosted by the League of United Latin American Citizens, or Lulac, which organizers said could draw 15,000 to 20,000 people to a convention center in this lakeside city.

“What we’re seeing with our community at this very moment in America’s history is a high level of fear,” said Sindy Benavides, the chief executive officer of Lulac. “And for many in our community, it’s really looking at the fact that who gets elected matters. Who sits at the local, at the state, at the national level, matters.”