During Donald Trumps rally at Madison Square Garden on Sunday, campaign surrogate Elon Musk pitched an eyebrow-raising $2 trillion budget cut.

Billionaire businessman Howard Lutnick introduced fellow billionaire Musk during the rally and asked Musk about cutting spending.

How much do you think we can rip out of this wasted $6.5 trillion Harris-Biden budget? Lutnick said, having complained that the government only took in only around $4.5 million in taxes.

I think we can do at least $2 trillion, Musk said.

Trump has promoted Musk as someone who could identify wasteful federal spending, but a $2 trillion cut would amount to almost a third of the budget and crush a range of popular programs especially if popular ones like Social Security are exempted.

Though its typical for Republicans to say they support spending cuts and balanced budgets, Trump has never championed fiscal austerity. Since entering politics as a presidential candidate in 2015, he has steered the Republican Party away from its past support for cuts to retirement programs like Social Security and Medicare.

Since Social Security and Medicare by themselves amount to about a third of federal spending, holding them harmless from an across-the-board reduction means cuts to other programs would have to be much deeper.

The problem with people proposing budget cuts this big is that they start saying, Well, I obviously wouldnt do that to my program here. And then, all of a sudden, to make the math work, it has to be impossibly large [cuts] for everything else, Bobby Kogan, a budget expert with the liberal Center for American Progress Action Fund, said in an interview.

The federal government spent about $6.8 trillion in the 2024 budget year which ended Sept. 30 but only brought in about $4.9 trillion, resulting in the third largest deficit ever, at $1.8 trillion, according to Treasury Department data . Social Security outlays totaled $1.5 trillion, while Medicare spending was $874 billion, the same amount as defense spending for the year. Net interest payments on the debt amounted to $881 billion.

Those four categories totaled a bit over $4.1 trillion of the governments $6.8 trillion in spending. Put another way, if those politically sensitive programs were exempt from cuts or in the case of interest spending, unable to be cut without triggering a debt crisis there would only be about $2.7 trillion from which Musk would be trying to find $2 trillion in cuts.

Kogan said the cuts to other programs get progressively deeper the more items are kept off the chopping block. Exempting Social Security, he said, would result in a 44% cut for all other programs. Adding Medicare to the exemption list with Social Security would make the across-the-board cuts bigger, at 56%. If defense were added to the list of things protected from cuts, Kogan said the cuts to other programs would rise even further, to 77%.

And if veterans programs were also protected, in addition to Social Security, Medicare and defense, the cuts to other programs would rise to 89%, Kogan said. The magnitude of the reductions would make them politically impossible.

Thats obviously absurd, right? he said. Its an absurd policy, its an absurd stance, its an absurd recommendation. Its from someone whos fundamentally unserious and is not willing to actually grapple with the difficulties here.

Musk has jokingly pitched himself as a Trump cabinet secretary leading a new Department of Government Efficiency, the agency names initials spelling DOGE, a reference to an old internet meme and cryptocurrency that Musk has frequently promoted. Its not clear if Trump would actually push for a new government agency or nominate Musk to lead it.

Still, Lutnick, the co-chair of Trumps presidential transition team, rhapsodized Sunday about the federal government of the early 1900s, a time when there were no income taxes and no Social Security or Medicare. He has described himself and Musk as the co-founders of DOGE , an idea he repeated on Sunday.

Musk was happy to play along, to cheers from the crowd.

Your moneys being wasted and the Department of Government Efficiencys going to fix that, Musk said Sunday.