Joe Biden accused Donald Trump on Monday of wanting to slash Social Security, setting off frantic pushback by the former president’s team, which has long viewed the program as a political vulnerability for Republicans.

Biden seized on remarks from Trump suggesting there were ways to deal with a program “in terms of cutting” to advance a key election-year attack. During a stop in New Hampshire, he highlighted Trump’s comments as a clear sign that Republicans “want to put Social Security and Medicare back on the chopping block.”

“Bottom line is, he’s still at it,” Biden said. “I’m never going to allow that to happen.”

The broadside represented one of the first major policy clashes of the nascent general election and a swift attempt by Biden to revive a major political fight over the fate of Social Security — an issue the campaign hopes to make central in the election.

It came hours after a CNBC “Squawk Box” interview, during which Trump was asked if he’d changed his “outlook” on entitlement programs. His reply focused largely on waste and managerial inefficiency but was meandering enough to leave an opening for the White House to insist that he was laying out a threat to the hugely popular social insurance program.

“So first of all, there is a lot you can do in terms of entitlements, in terms of cutting,” Trump told CNBC. “And in terms of, also, the theft and the bad management of entitlements — tremendous bad management of entitlements — there’s tremendous amounts of things and numbers of things you can do.”

Trump’s campaign argued that Biden and Democrats had ripped his remarks fully out of context. But in a sign of how sensitive they view the topic, the Republican National Committee issued a steady stream of posts on Monday digging up old clips of then Senator Biden opening the doors to Social Security reform. And in a statement, Karoline Leavitt, the campaign’s national press secretary, argued that it was the president, not Trump, who posed the bigger threat.

“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,” Leavitt said. “The only candidate who poses a threat to Social Security and Medicare is Joe Biden — whose mass invasion of millions of illegal aliens will, if Biden allows them to stay, cause Social Security and Medicare to collapse.”

Few topics are as electorally potent as Social Security, which is often dubbed the third rail of politics. And Trump himself is fully aware of it.

He has long sought to project himself as a protector of Social Security and Medicare. He was highly critical of House GOP austerity budgets during the Barack Obama years. And among the first policy issues he touted as a candidate this cycle was that congressional Republicans should not demand Social Security cuts during negotiations with Biden over raising the debt ceiling.

During the primary he used Social Security as a cudgel against his opponents. His campaign spent about $937,000 on ads in New Hampshire focusing on Nikki Haley’s support for Social Security reform. It was his biggest ad expenditure in the state, according to Ad Impact.

Biden has also vowed to shield the entitlement program, arguing that he’s stood as a bulwark throughout his presidency against Republican plans to cut the benefits that older Americans relied on. The White House hammered the GOP last year’s debt ceiling showdown over some lawmakers’ suggestions they could use the crisis to force entitlement cuts. Instead, Biden ultimately extracted a promise that Republicans would not touch Medicare and Social Security as part of a deal.

The administration has since sought fresh opportunities to highlight its work to guard Social Security, believing that it’s critical to Biden’s reelection effort that he maintain the upper hand on the issue.

During his State of the Union speech, Biden warned that Republicans may seek to “cut Social Security and give more tax breaks to the wealthy.” The line prompted immediate protests from GOP lawmakers in the audience. But by Monday, Trump had handed Biden exactly the evidence he was looking for.

Meridith McGraw contributed to this report.