Senate leaders headed into the weekend with the fate of the broadest federal restriction on artificial intelligence in years still uncertain, as Democratic and Republican vote-counters worked through Saturday to lock down support for a Monday floor vote on the Sanders-Ocasio-Cortez moratorium bill.

The legislation, formally titled the Responsible Artificial Intelligence Compute Pause Act, would impose an 18-month moratorium on the construction of new frontier-model training data centers above a 50-megawatt threshold and require federal licensing of training runs that exceed a defined compute ceiling. Introduced in the Senate on March 26 by Sen. Bernie Sanders, I-Vt., and championed in the House by Rep. Alexandria Ocasio-Cortez, D-N.Y., the bill has drawn the most intense industry lobbying campaign Washington has seen since the 2017 net neutrality fight, according to several lobbyists tracking the effort.

Aides in both cloakrooms described the count as moving within a two-vote margin. A senior Democratic leadership aide, speaking on condition of anonymity to describe internal whip operations, said the caucus was carrying 43 firm yes votes, six holdouts and two members “openly persuadable.” Three Republican senators have publicly indicated they will support the bill, citing concerns about grid strain and water use in their states, and both independents are expected to vote yes.

“The math is real but it is not done,” the aide said. “We are spending every hour we have left.”

Republican leadership was equally direct. “This bill would not stop a Chinese chip from being made tomorrow, but it will stop an American data center from being built next year,” Senate Minority Leader John Thune, R-S.D., said in a statement Saturday morning, urging Democrats who had not yet committed to “look at what this does to the grid in their states and to the workers who depend on it.”

The five Democratic senators reported to be leaning no all represent states with significant data center or hyperscaler investment, and several have been publicly courted by industry executives in recent days. The bill’s authors have argued that the moratorium’s grid-relief and licensing provisions would actually accelerate, rather than block, the buildout of compute that meets clean-power and transparency requirements.

President Donald Trump, who has not formally threatened a veto, said Friday on the South Lawn that the bill “needs a lot of work” but that he would “see what the Senate does.” His ambivalence has frustrated some Republicans who were hoping for a sharper signal to harden the caucus against the measure. White House Press Secretary Karoline Leavitt declined Saturday to characterize the administration’s posture beyond saying that “any legislation affecting American technological leadership has to be looked at very carefully.”

Sanders, in a Saturday afternoon appearance at a community center in Manchester, N.H., framed the vote as a referendum on what he called the “energy capture” of the country’s electricity system by a handful of large technology companies. “These data centers are now consuming as much power as small cities and demanding more, and ratepayers are paying for it,” he said. “The Senate has a chance on Monday to say that the public has a voice in this.”

Ocasio-Cortez, who is leading the bill’s parallel House effort, met Saturday morning with members of the House Ways and Means Committee — the chamber where the bill is widely expected to face its hardest fight if it clears the Senate. “We are not pretending this is a small ask,” she told reporters afterward. “But the cost of doing nothing is much larger than the cost of pausing for 18 months while we get the rules right.”

Industry pressure has been ferocious. According to disclosure filings reviewed by congressional researchers, the major hyperscalers and their trade associations have logged more than 280 lobbying contacts with Senate offices in the past two weeks alone. Chief executives from at least three of the largest AI infrastructure firms were in Washington on Friday for what one Senate aide described as “speed-dating” sessions with undecided members.

“The industry is not arguing the merits at this point. They are arguing the consequences,” said Maria Cordero, a former Senate Commerce Committee counsel now at the Foundation for American Innovation. “Their pitch is: pass this and watch the buildout move to the UAE and Singapore.”

Opponents of the bill have also seized on the unrelated war in the Middle East to argue that the United States cannot afford to constrain a strategic technology sector during a period of geopolitical strain. Supporters counter that the war has, if anything, sharpened the case for slowing the grid demands of new training runs at a moment when energy markets remain volatile and U.S. military operations are themselves drawing on domestic power and fuel reserves.

Procedurally, the bill will need 60 votes to clear a cloture motion expected late Sunday or early Monday. If cloture is invoked, a simple-majority vote on passage would follow, likely Monday afternoon. Senate Majority Leader Chuck Schumer, D-N.Y., declined to predict the outcome Saturday but said he was “more confident than I was 48 hours ago.”

Even supporters acknowledged that passage in the Senate would be only the first hurdle. The bill faces a narrower path in the House, where the Ways and Means chairman has not yet committed to a timeline for a committee vote, and where centrist Democrats from data-center-heavy districts have signaled reluctance.

Senate aides said additional briefings for undecided members were scheduled through Sunday evening, with final whip counts expected to be locked in only hours before the cloture vote.