As Vice President Kamala Harris energized voters in Detroit and Atlanta this weekend, her most passionate supporters were just two miles from her residence in Washington, D.C., where Howard University, her alma mater, marked its centennial homecoming.

Known affectionately as “The Mecca” by its graduates, this historically Black institution hosted a week of activities that attracted thousands of alumni nationwide for festivities and a concert leading up to a key football game. Ms. Harris opted not to attend this year, choosing instead to campaign in crucial battleground states like Michigan and Georgia, while sidestepping the complex security challenges that accompany a sitting vice president and presidential candidate at a major event.

Nevertheless, the anticipation for the possibility of the nation’s first Black woman and H.B.C.U. graduate becoming president was unmistakable both on and off campus. Students eagerly took photos with cardboard cutouts of Ms. Harris in the university’s main square. Vendors lined Georgia Avenue, the main thoroughfare leading to Howard, selling T-shirts featuring Ms. Harris’s image and memorable quotes. Following the annual parade, the Harris campaign organized a rally for alumni.

Yet, as the presidential race enters its final weeks, there is palpable anxiety surrounding the vice president’s candidacy. While many alumni expressed joy at seeing one of their own leading a presidential ticket, they couldn’t ignore the slim margins in the race, prompting many to step up their efforts on her behalf.

“I’m bubbling with excitement for our fellow Bison, who is running for the most powerful position in this incredible country,” Christina Weaver Jackson, host of a “Bison for Kamala” fundraiser in D.C., told attendees on Thursday. “But I’m also quite anxious.”

Actor Anthony Anderson, also a Howard graduate, headlined the fundraiser. He pointed out QR codes with fundraising links around the venue and reminded guests that their most crucial contribution was networking—specifically, persuading less enthusiastic voters in their circles to cast ballots, ideally for their fellow alumna.

“I believe Kamala Harris is on the right side of politics in this election compared to the other candidates,” Mr. Anderson stated during an interview at the fundraiser. “And it’s not just because she’s Black, a woman, or a Bison.”

Presidential candidates have historically sought to connect themselves to H.B.C.U.s, often highlighting their efforts to support these institutions as examples of their commitment to Black voters. This election cycle, both Donald J. Trump and Ms. Harris have touted increased funding for H.B.C.U.s under their administrations, with Ms. Harris emphasizing the White House’s $17 billion investment in a letter to the university on Saturday.

With Ms. Harris at the helm of the Democratic ticket, H.B.C.U.s have become vital organizing hubs. Her campaign has taken note and launched an H.B.C.U. homecoming tour this month, deploying representatives to historically Black campuses in battleground states to galvanize Black voters.

Jonathan Barnes, a 33-year-old Ph.D. student at Howard who was seen with pro-Harris signs, declared his support for her. He recognized, however, that some young voters remain hesitant to back her.

“My personal view is that Kamala is our best option right now,” he said, encouraging those uncertain about her to “give her a chance and rethink their perspective.”

Ms. Harris’s candidacy has also spurred the formation of various fundraising initiatives aimed at mobilizing Black voters on her behalf. The “Bison for Kamala” group is expected to raise over $250,000 for her campaign by the end of homecoming weekend, according to co-founder Stefanie Brown James, who also co-founded the Collective PAC to support Black candidates.

Other organizations, including the Divine Nine Black Greek-letter societies, have committed to enhancing their voter engagement efforts this year. Alpha Kappa Alpha, the sorority Ms. Harris joined while at Howard, formed a PAC to contribute directly to her campaign after partnering with other Black sororities and fraternities. This PAC has raised over $900,000 in the past two months, as reported by the Federal Election Commission, with many donations made in amounts of $19.08—symbolic of the organization’s founding year.

Having graduated from Howard in 1986, the university has served as a supportive backdrop throughout her political ascent. After being chosen as President Biden’s running mate in 2020, she set up a temporary office in Founders Library on campus. Following Mr. Biden’s withdrawal from the race in July, she made calls to supporters while wearing a Howard sweatshirt. During her campaign, she even practiced for the only debate at the university’s Cramton Auditorium.

On Saturday, the Harris campaign distributed water bottles, signs, and T-shirts as alumni flocked to the main yard. Organizers encouraged attendees to knock on doors and make calls for Ms. Harris, providing cards for voters to pledge their commitment to participate.

Despite a strong network of student and alumni support for her campaign, Howard University itself has been more cautious about endorsing her publicly. The institution has had to carefully navigate its support for its alumni in politics without backing any particular candidate, as doing so could jeopardize the federal funding that comprises over a third of its budget.

However, many Howard alumni have seized on Ms. Harris’s candidacy as an opportunity to express pride in their university and one of its most prominent graduates.

“I can’t say ‘I go to Howard’ enough,” said Tonya McCray, a labor union employee who has been canvassing for Ms. Harris in her hometown of Waldorf, Md., for weeks while wearing a Howard shirt emblazoned with “VOTE.” She mentioned trying to maintain a positive outlook despite tight polling numbers and some unkind interactions with voters. Still, she remained confident in Ms. Harris’s chances.

“Setting aside the fact that she could become our first Black female president, her accomplishments so far just bolster my confidence even more,” Ms. McCray stated.