Vice President Kamala Harris criticized former President Trump's proposal to eliminate income taxes on Social Security benefits during a campaign stop on Monday, citing a nonpartisan budget report that claimed Trump's plan would "dramatically worsen Social Security's finances."

The Committee for a Responsible Federal Budget (CRFB), a nonpartisan policy think tank, published a report Monday claiming Trump's plans to "eliminate taxation of Social Security benefits, end taxes on tips and overtime, impose tariffs, and expand deportations would all widen Social Security's cash deficits."

"What I think most of us know is that we have many, many seniors in our country, their Social Security check is their only form of income," Harris said during a campaign stop in Michigan Monday. "It's everything and the only thing they have to live on: to pay rent, groceries, all of that. So we must protect Social Security."

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If elected, the policy think tank also found that Social Security's cash shortfall could increase by $2.3 trillion through 2035. This change would push the program's insolvency date up from 2034 to 2031, meaning the next president will need to deal with this issue sooner than expected. If these changes happen, people could face a 33% cut in their benefits by 2035, compared to a 23% cut projected earlier, the report noted.

Additionally, the annual shortfall is expected to rise by about 50% in 2035, going from 3.6% to 4% of payroll. To fix the long-term funding issues for Social Security, the report suggests there would either need to be benefit cuts by one-third or revenue increases of about 50%.

But a former Trump administration adviser who worked on Social Security policy told Fox News Digital in an interview that "what the Biden Harris folks are doing to mismanage the agency is bleeding money in over payments."

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"And now sort of waving everyone's over payment, as what [Commissioner Martin O'Malley] is doing, I think is a lot more reckless and doing a lot more harm to the trust fund than proposing even these ideas," the source said.

"Obviously every candidate is going to be very afraid to touch it," he added. "But what I will also say, and I actually helped work on some of these, is that Trump did propose tens of billions of dollars in savings in the Social Security Program generally in his first two budgets. And he did that not by going after seniors, but he did that by trying to modernize disability. And you know, that doesn't necessarily help the trust fund issue real largely, but it does help sort of fix the Disability Trust Fund and start to bring some of the finances under control a little bit."

Harris later told CNN she believed Trump was "hostile" toward the "notion and purpose of Social Security" and that it would be "catastrophic" if the SS trust fund was insolvent in the next few years.

Meanwhile, Trump campaign spokeswoman Karoline Leavitt said in an emailed response:

"President Trump delivered on his promise to protect Social Security and Medicare in his first term, and President Trump will continue to strongly protect Social Security and Medicare in his second term. The only candidate who poses a threat to the solvency of Social Security is dangerously liberal Kamala Harris - whose mass invasion of millions of illegal aliens will, if they are allowed to stay, cause Social Security to buckle and collapse. By unleashing American energy, slashing job-killing regulations, and adopting pro-growth America First tax and trade policies, President Trump will quickly rebuild the greatest economy in history and put Social Security on a stronger footing for generations to come, all the while eliminating taxes on Social Security for America's well-deserving seniors."

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The annual Social Security trustees' report over the summer said the Old-Age and Survivors Insurance (OASI) trust fund is on track to reach insolvency in 2033, at which point benefits would be cut by 21%.

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The U.S. has an aging population, more than 67 million of whom receive Social Security benefits. And the older an American is, the more likely they are to vote, so many politicians shy away from discussing reforms of the program at all.

But if no reforms are made, the same Americans who receive Social Security benefits now - particularly those who rely on the benefits - face a significant threat to their income come 2033.

Fox Business's Breck Dumas contributed to this report.