At a campaign rally in April, President Biden told a Wisconsin crowd about his latest “life-changing” plan for student loan cancellation, promising financial relief for more than 30 million Americans.

But Vice President Harris has steered clear of the issue at her political events since replacing Mr. Biden as the Democratic nominee for president. The vice president’s platform mentions it just twice, and with no specific plan. Courting moderate voters, Ms. Harris has focused on policies targeting Americans without a college degree.

“For far too long, our nation has encouraged only one path to success: a four-year college degree,” Ms. Harris said in September in Wilkes-Barre, Pennsylvania. “Our nation needs to recognize the value of other paths.”

In the span of just a few years, student loan cancellation has gone from a pillar of the Democratic Party to a political liability. Once seen as a sure-fire way to energize young voters, the issue has now become a bludgeon wielded by critics who say it heaps advantage on elites and comes at the expense of those who repaid their loans or did not attend college.

The issue came up just once in the September presidential debate, when President Trump hammered Ms. Harris and Mr. Biden for failing to deliver their promise of widespread cancellation. The former president called it a “total catastrophe” that “taunted young people.”

“They didn’t even come close to getting student loans” cancelled, Trump said.

Mr. Biden, who once questioned the legality of mass student loan forgiveness, campaigned on the issue after liberals like Senator Sanders made it a mainstream idea. But as president, Mr. Biden has faced relentless challenges from Republican opponents. For the roughly 42 million people with federal student loans, hope of having them forgiven has turned into resignation and disillusionment.

Mr. Biden’s first plan to cancel up to $20,000 for millions of people was blocked by the Supreme Court last year. A second, narrower plan has been halted by a federal judge after Republican-led states sued. A separate policy intended to lower loan payments for some borrowers has been paused by a judge, also after Republican-controlled states challenged it.

On Friday, the Biden administration moved ahead with yet another attempt at student loan cancellation, this one focused on Americans who face heavy financial burdens beyond their student loans. It faces an uncertain future, arriving less than two weeks before the November 5 election.

The legal uncertainty has probably contributed to Ms. Harris’ de-emphasis of cancellation, said an education program director at the think tank Third Way, Michelle Dimino. It’s also an issue her base is familiar with, she added.

“There’s not too much new she can offer before we know what will happen in the courts,” Ms. Dimino said. When Mr. Biden first pitched broad cancellation, it was something that hadn’t been tried. “Now, it’s a totally different landscape than it was in 2020, when it was a clean slate.”

Ms. Harris’ silence also signals the political risks, especially in a tight election. Any new promise of loan cancellation would energize Republicans who have made it a rallying cry. For voters who could benefit from cancellation, it’s a promise they have heard before.

“The Harris campaign has realized this is not necessarily a winning political issue,” said a senior fellow at the American Enterprise Institute, Preston Cooper. “The student loan agenda is in tatters and hasn’t really helped them win any votes.”

Even moderate Americans appear skeptical of student loan forgiveness. A June poll from the University of Chicago Harris School of Public Policy and The Associated Press-NORC Center for Public Affairs Research found that 3 in 10 American adults said they approve of Mr. Biden’s work on student debt, and it wasn’t much better among those repaying loans. Slightly more than half of Democrats said they supported the president’s work, while 18 percent of independents said the same.

The Harris campaign declined to give specifics or answer questions about her cancellation plan.

Her platform mentions student loans only after a full page of policies targeting workers without degrees. At the September rally in Pennsylvania, Ms. Harris drew applause when she said she would get rid of unnecessary degree requirements for federal jobs. She did not mention student loans in her 20-minute speech.

“Requiring a certain degree does not necessarily talk about one’s skills,” Ms. Harris told the audience at Wilkes University, a private college in northeast Pennsylvania.

Ms. Harris’ comments echo a traditional Republican talking point that has increasingly been embraced by Democrats as more Americans question the value of a college degree.

“Student loan forgiveness is … maybe alienating some of the support that Harris is hoping to get from the non-college-educated,” said a research fellow at the libertarian Cato Institute’s Center for Educational Freedom, Andrew Gillen. “These kinds of polarizing topics are poisoning the well for other things that have bipartisan support. Once issues like student loan forgiveness are put to rest, I think a lot more of that bipartisan agreement will emerge.”

In his platform, Trump said he will “support the creation of additional, drastically more affordable alternatives to a traditional four-year college degree.” It doesn’t mention loans. Trump has opposed cancellation, saying it’s illegal.

“President Trump will implement real solutions to make education, housing, and the cost of living affordable again for young people so they can live the American dream,” said a national press secretary for Trump’s 2024 presidential campaign, Karoline Leavittt.

As attorney general in California, Ms. Harris led efforts to penalize for-profit colleges for defrauding borrowers. As a presidential candidate in 2019, she proposed a narrower path to loan forgiveness than those pushed by Mr. Sanders and Senator Warren. Harris’ plan would have provided $20,000 in relief to any federal Pell Grant recipient who started a business in a disadvantaged community and kept it running for three years.