The U.S. Senate on Tuesday narrowly passed a sweeping two-year moratorium on the training of new frontier artificial intelligence models, sending the contentious Sanders-Ocasio-Cortez bill to a deeply uncertain reception in the House and triggering an immediate lobbying surge by the country’s largest technology companies.

The final tally was 52-48. Three Republicans and both independents crossed the aisle to join all but five Senate Democrats, producing a coalition that aides on both sides described as fragile but durable enough to clear the chamber after nearly nine hours of floor debate that stretched past midnight Monday and resumed shortly after the morning prayer.

The legislation, introduced March 26 by Senator Bernie Sanders of Vermont and Representative Alexandria Ocasio-Cortez of New York, would impose a 24-month pause on the training of any AI system above a defined compute threshold, require federal licensing for new data center buildouts exceeding 50 megawatts, and direct the Energy Department and the National Institute of Standards and Technology to draft binding safety, labor and environmental standards before the moratorium could lift. A reconciliation provision attached late in committee would also claw back roughly $4.2 billion in unspent CHIPS Act incentives tied to large model training, redirecting the funds toward grid hardening.

“This vote is a beginning, not a victory lap,” Sanders told reporters in the Capitol’s Ohio Clock corridor minutes after the gavel. “We have said clearly that the American people, not five companies in California, will decide what this technology does to our economy, our power grid, and our democracy.”

Senate Majority Leader Chuck Schumer, who had publicly opposed bringing the bill to the floor as recently as two weeks ago, allowed the vote after what aides characterized as a series of tense caucus meetings. Schumer voted yes. Senator Mark Kelly of Arizona, Senator Jacky Rosen of Nevada, Senator Mark Warner of Virginia, Senator Jon Ossoff of Georgia and Senator Maggie Hassan of New Hampshire were the five Democrats voting no, each citing concerns about national security implications and the bill’s effect on competitiveness against Chinese model developers.

The three Republican yes votes came from a small bloc that had been telegraphing support for weeks. They argued, in floor speeches that drew sharp rebukes from party leadership, that unchecked data center expansion was straining rural electric cooperatives and that the moratorium’s grid provisions would protect ratepayers in their states. Both independents, who caucus with Democrats, voted yes.

Senate Minority Leader John Thune of South Dakota called the bill “an economic unilateral disarmament” and predicted it would not survive the House. “We are handing Beijing a two-year head start, and we are doing it in the middle of a war,” Thune said, referring to the ongoing U.S.-Iran conflict. “The Senate has voted to make America slower, poorer and more dependent.”

The White House response was notably restrained. Press Secretary Karoline Leavitt, in a brief statement issued at 11:42 a.m., said only that President Trump “will review the legislation if and when it reaches his desk” and reiterated the administration’s preference for “a competitive American AI sector, not a frozen one.” Two senior administration officials, speaking on condition of anonymity to describe internal deliberations, said the president has privately expressed sympathy for the bill’s grid and energy provisions while remaining skeptical of the broader training pause. A veto, those officials said, was not being ruled in or out.

Industry reaction was swift and uniformly negative. The Chamber of Progress, the trade group representing the largest hyperscalers, called the vote “a profound policy error.” A coalition letter circulated within an hour of the vote and signed by the chief executives of seven major AI and cloud companies urged House leadership to “reject this measure in its current form and convene a serious bipartisan process.” Shares of the largest model developers and cloud providers fell sharply in midday trading before paring losses on the assumption that the House would block the bill.

“The market is pricing in a roughly one-in-three chance this becomes law,” said Priya Ramaswamy, a tech policy analyst at Beacon Hill Strategies. “That probability is high enough to spook investors and low enough that no one is unwinding positions. Everything now turns on Ways and Means.”

The bill heads next to the House Committee on Ways and Means, which has jurisdiction over the CHIPS Act clawback provision and which has scheduled markup hearings to begin April 14. Chairman Jason Smith of Missouri has signaled deep skepticism, and a head count by House Democratic leadership over the weekend suggested the committee’s 24-21 Republican majority would likely produce a party-line defeat. Two committee Democrats are also viewed as potential defectors.

Ocasio-Cortez, speaking from the House side of the Capitol Tuesday afternoon, said she would spend the next two weeks “in every member’s office that will have me, and a few that won’t.” She said the bill’s coalition of labor unions, rural electric cooperatives, civil rights organizations and a growing bloc of AI safety researchers had grown stronger in recent weeks, not weaker. The AFL-CIO endorsed the bill last Thursday; the National Rural Electric Cooperative Association issued a supportive statement Monday night.

Outside the Capitol, a crowd of roughly 800 supporters gathered on the East Front in a light rain, organized by a coalition that included the Communications Workers of America and several climate groups. A smaller counter-protest of about 150, organized by libertarian and free-market organizations, assembled on the West Front.

Senate aides said the chamber would now turn its attention to a supplemental defense appropriations package tied to the Iran conflict, expected on the floor Wednesday. House leadership has not yet set a date for floor consideration of the AI bill, and aides on both sides of the Capitol said that a Ways and Means vote, expected by April 22, would likely determine whether the measure ever reaches the House floor at all.