Joy, vindication and anxiety: Democrats absorb a consequential moment.

In some ways, it was the turn of events Democratic voters had dreamed of and some of the party’s lawmakers had long demanded: After years of telling lies, shattering norms, inciting a riot at the Capitol and being impeached twice, Donald J. Trump on Thursday became the first former president to face criminal charges.

“We’ve been waiting for the dam to break for six years,” declared Carter Hudgins, 73, a retired professor from Charleston, S.C. “It should have happened a long time ago,” added his wife, Donna Hudgins, 71, a retired librarian.

But as the...