“What was the point?” asked Motley, 23, a grocery store clerk. “We made history, but I don’t see change.”

On Jacksonville’s north side and in other struggling urban neighborhoods across the country, where Barack Obama mobilized large numbers of new African American voters who were inspired partly by the emotional draw of his biography, high hopes have turned to frustration: Even a black president was unable to heal places still gripped by violence, drugs and joblessness.

The dynamic, made prominent in recent months after unrest in Baltimore and Ferguson, Mo., sets up a stark challenge for Hillary Rodham Clinton, the Democratic presidential front-runner.

While supporting Obama became a cause for many here rather than a typical campaign, Clinton faces a higher bar in making a case that she, too, can be a transformative figure.