WASHINGTON — Sen. Elizabeth Warren of Massachusetts is unveiling a proposal to wipe out student debt for millions of borrowers, making her the only major 2020 presidential candidate to advance such a plan to relieve the growing burden of higher-education loans on Americans and the economy.

The proposal would cancel up to $50,000 in debt for people with annual household income under $100,000. Beyond that income threshold, smaller amounts of debt would be canceled, but no one with more than $250,000 in household income would be eligible.

To keep students from accumulating more debt in the future, Warren also proposes making two- and four-year public colleges tuition free, according to a plan unveiled in advance of a Monday evening CNN town hall focused on issues of interest to young voters.

With a price tag of $1.25 trillion over 10 years, Warren’s higher-education initiatives up the ante on an issue that most 2020 Democratic presidential candidates have been trying to address.

At issue is the top economic challenge for a key Democratic constituency — millennial voters, many of whom have gone to college and left school during a decade that has seen an explosion of student borrowing. Student loan debt has more than doubled, to about $1.5 trillion, over the last decade, according to a Federal Reserve report that found the trend has contributed to declining rates of homeownership.

“The time for half measures is over,” said Warren in a post on Medium describing her proposals. “My broad cancellation plan is a real solution to our student debt crisis. It helps millions of families and removes a weight that’s holding back our economy.”

The high-dollar proposal will surely face push back from Republicans but also from some Democratic rivals. Sen. Amy Klobuchar, D-Minn., has said she opposes tuition-free four-year public college, although she favors free community college. Pete Buttigieg, mayor of South Bend, Ind., has objected to broad student-debt cancellation, preferring more-targeted debt relief.

Warren said the cost of the program would be covered by some of the $2.75 trillion in revenue that would be raised from the “wealth tax” she has proposed — a 2 percent tax on Americans with assets worth more than $50 million, with an additional 1 percent surcharge on wealth over $1 billion.