Trump Is Speaking at an H.B.C.U. His Allies Will Outnumber Students.

COLUMBIA, S.C. — President Trump and his allies have billed his speech at a historically black college here on Friday afternoon as a chance to step outside the friendly confines of his supporter base and pitch his administration’s actions on criminal justice reform and black employment directly to a black audience.

But in the invitation-only room of about 300 people, only about 10 students will be admitted from Benedict College, which is hosting the event, said Mayor Stephen K. Benjamin of Columbia. More than half of the seats were reserved for guests and allies of the administration, organizers said.

The ticket distribution was first reported by McClatchy DC.

Mr. Trump is scheduled to open a three-day event at the college, billed as the “Second Step Presidential Justice Forum.” Leading Democratic presidential candidates will attend the forum on Saturday and Sunday to pitch their criminal justice plans, including former Vice President Joseph R. Biden Jr., Senator Elizabeth Warren of Massachusetts and Senator Bernie Sanders of Vermont.

Mr. Trump signed the bipartisan First Step Act in December, which has helped thousands of federal inmates secure early release under new sentencing guidelines and has been a key part of the White House’s pitch for black support. The Trump administration has hailed the act as one of its signature legislative accomplishments.

About one hour before Mr. Trump’s scheduled appearance, more than 100 anti-Trump protesters gathered near the campus perimeter, some wearing shirts covered in pictures of peaches to signify the ongoing impeachment inquiry in the House of Representatives.

The protest included few Benedict students; it mostly comprised local residents and staff members of the state Democratic Party and some of the Democratic presidential campaigns, who were preparing for their candidates to arrive on Saturday.

Tim Bupp, a 62-year-old South Carolina pastor, held a sign that showed a lynched black person hanging from a tree. It was a reference to Mr. Trump’s tweet this week comparing the Democrats’ impeachment inquiry to a lynching.

“The fact that he compares the inquiry to a lynching and then has the audacity to come to a black college? Insane,” said Pastor Bupp, who is white. “He doesn’t even apologize. He just doubles down.”

Michelle Thomas, a 42-year-old Columbia resident, said Mr. Trump’s lynching remark motivated her to protest.

“That was the final straw for me,” said Ms. Thomas, who is black. “I knew I needed to take more actions against him.”

She said she was also upset that Senator Lindsey Graham, one of her state’s two Republican senators, had defended Mr. Trump’s remarks. “Trump’s actions got Trump in this situation,” she said. “No one else.”

In the Democratic primary, black voters play a critical role in selecting the party’s nominee, especially in South Carolina, an early-voting primary state where they make up more than half the party’s electorate. But even the slightest downturn in black turnout in a general election can be fatal for a Democratic presidential candidate, and Mr. Trump and his allies have expressed some hope that they can peel off enough support from black voters — or keep them home altogether — to make an impact in battleground states in 2020.

In 2016, a decrease in black turnout in cities such as Milwaukee, Detroit and Philadelphia helped Mr. Trump win key swing states by razor-thin margins, propelling him to an Electoral College victory.

With that political backdrop in mind, overhauling the criminal justice system has, in recent years, been one of the rare areas of some bipartisan agreement in an increasingly polarized Congress, and that partial consensus has spilled into the presidential race. Democrats making the progressive argument for reform have cited the system’s disproportionate impact on black, Latino and Native American communities.

Conservatives, while avoiding portraying the system as inherently prejudiced, have often focused on the financial burden mass incarceration places on governments.

The Trump administration has sought to support historically black colleges and universities, increasing federal support by 14.3 percent. And Mr. Trump spoke to black educators last month at the National Historically Black Colleges and Universities Week conference.

But Mr. Trump has also made attacks on lawmakers of color central to his re-election strategy. This summer, for example, he lashed out at Representative Elijah E. Cummings on Twitter, referring to Mr. Cummings’s majority-black district in Baltimore as a “disgusting, rat and rodent infested mess” where “no human being would want to live.”

Mr. Cummings, who died last week, on Thursday became the first African-American elected official to lie in state in the United States Capitol.

Leaders of historically black colleges and universities have long enjoyed close relationships with both Republican and Democratic presidential administrations, even as their institutions face increasingly dire financial straits. Born of a time of segregation when black Americans were forced to educate themselves, the schools have produced black leaders for more than a century, including politicians such as Senator Kamala Harris of California and Mr. Cummings, who both attended Howard University.

In 2017, when several presidents of black colleges met with Mr. Trump in the Oval Office, many faced backlash from their student bodies. At Howard, founded 150 years ago in Washington, campus buildings were tagged with graffiti that denounced the school’s president and said “Make Howard black again.”

Campus leaders defended themselves by pointing to their pocketbooks, and the need to secure federal funds to maintain viability.

“You need to get to the president to impact his budget if you hope to get your financial support from Congress,” said Johnny C. Taylor Jr., president and chief executive of the Thurgood Marshall College Fund, which represents 47 black colleges and universities that receive public funding.