Vermont Sen. Bernie Sanders called on President-elect Donald Trump follow through on a raft of pledges—including heavy federal spending on Medicare, Medicaid, Social Security and infrastructure—that he made as candidate, in the face of the Republican Congress’s budget-slashing ambitions.

Trump split with decades of fiscally conservative GOP dogma during his erratic run at the presidency by promising to leave entitlement outlays untouched and to sink billions into the country’s bridges, roads and water systems. Now, after his unpredicted victory ushered in a Republican sweep of D.C., House Speaker Paul Ryan has signaled his intention to enact his own vision of a drastically shrunken federal government—which includes turning Medicare into a private voucher system.

Sanders, who Trump often quoted approvingly in the last leg of the campaign, insisted the incoming commander-in-chief resist any such efforts.

“We’re going to hold him accountable,” Sanders said to an explosion of applause from the audience at George Washington University. “Mr. Trump said, unlike many Republicans, the vast majority of Republicans, he said we—he—will not cut Social Security, Medicare and Medicaid.”

In the third debate, Trump shocked Republican policy wonks by suggesting he would deal out massive Medicaid block grants to the states to provide insurance to people who would lose their coverage if he succeeded in repealing the Affordable Care Act, popularly called Obamacare. In his first interview since clinching the Electoral College—Hillary Clinton, who Sanders ran against then endorsed, won the popular vote—Trump told 60 Minutes he had softened his position on the program, and would only eliminate portions of it.

Sanders demanded Trump not recant his stances on entitlement programs, the largest and fastest growing portion of the federal budget.

“Number one, says Mr. Trump, is no cuts to Social Security, Medicare and Medicaid,” the self-described democratic socialist said. “That is what he said. And pay attention to see what he now does. The question that will be resolved, pretty quickly, is whether or not everything he was saying to the working families of this country was hypocrisy, was dishonest, or whether he was deceiving. And we will find that out soon enough.”

The Vermont lawmaker similarly remembered the Queens-born businessman’s calls to plunge $1 trillion into the country’s infrastructure. Superficially, this resembles the plan Sanders presented in the Democratic primary, though Trump’s vision calls for obtaining private financing through a massive tax break for investors.

Nonetheless, the leftist legislator spoke glowingly of the idea—if the new president actually pursues it.

“That is exactly what we should be doing, and we create millions of good-paying jobs if we do that,” said Sanders. “Mr. Trump, that’s what you said on the campaign trail, that’s what we look forward to seeing from you.”

The senator also pointed up Trump’s proposal to provide new mothers with six weeks of paid maternity leave, and his inconsistent and often self-contradicting calls for a higher minimum wage and for sundering investment banks from commercial lending operations. Ditto for the mogul’s insistence that the country must review and revise and possibly even scrap a number of global anti-tariff accords, including the North America Free Trade Agreement.

“What you will see on Capitol Hill is many Democrats will be prepared to work with Mr. Trump, if he turns out to be sincere about the promises he made during the campaign,” said Sanders. “If those promises turn out to be hollow, if they were nothing more than campaign rhetoric, we will not only oppose his economic policies, we will expose those hypocrisies as well.”

The independent lawmaker caucuses with the Democrats, and voted with his 47 colleagues in the conference this morning to raise Sen. Charles Schumer to the perch of minority leader, replacing the retiring Harry Reid. So long as the Republicans hold fewer than 60 Senate seats, and the current filibuster rules remain in place, the majority party will need Democratic votes to close discussion on any policy matter.

Sanders also used his speech tonight, broadcast via the Facebook page of his group Our Revolution, to lash out at the president-elect’s choice of Breitbart News head Stephen as his chief political strategist and counsel. Bannon has advertised Breitbart as “the platform for the alt-right,” a fringe group of loosely affiliated extremists with racist views.

“We will not be involved in the expansion of bigotry, of racism, sexism, xenophobia,” he said. “The president of the United States should not have a racist at his side, plain and simple.”

Disclosure: Donald Trump is the father-in-law of Jared Kushner, the publisher of Observer Media.