President Donald Trump's Big, Beautiful Bill passed a major procedural milestone at 11:07 p.m. Saturday night, when the United States Senate voted 51-49 to invoke cloture. Cloture is an essential step in the upper legislative chamber, limiting the remaining time members have to debate and starting the countdown to when they can vote on passage.

The late-night vote was a close call on a lengthy and arduous process. Vice President J.D. Vance was on hand at the Capitol from around 8:20 p.m. on, in case his vote was needed. In his Executive Branch capacity, Vance serves as president of the Senate -- a constitutional role that empowers him to preside over Senate proceedings and cast the tie-breaking vote in cases of gridlock.

In the end, his vote was not needed for this hurdle; Republican Sen. Ron Johnson (Wisc.) -- a Trump ally but also a fiscal hawk and vocal critic of the bill -- switched his vote to a yes, allowing cloture to proceed. Republican Sens. Rand Paul (Ky.) and Thom Tillis (N.C.) voted no. Tillis's no vote was based on objections to restrictions the bill will place on states gaming their end of the 50-50 Medicaid expenses split with the federal government. Paul, a D.C. libertarian, was never counted on for a "yes."

RELATED: The Medicaid tax trick pitting old-guard Republicans against the populist new right

The Big, Beautiful Bill, or H.R. (House Resolution) 1, as it's officially designated, funds key aspects of the White House's agenda, from deportations to border enforcement, making his first-term tax cuts permanent and adding no taxes on tips or overtime. It will be the signature legislative accomplishment of Trump's first year back in the Oval Office.

Cloture is a Senate procedure that limits further debate on a bill -- in this case, to 10 hours each, for the Republican and Democratic parties. Democrats drew the process out further by exercising their right to have Senate clerks read the bill first -- no small process for a 940-page bill. At 7:35 a.m., the Senate press gallery tweeted clerks had completed 470 pages of reading, or half of the bill, in the preceding 8 hours and 27 minutes -- setting them up for completion early Sunday evening.

Once they're done, Republicans are expected to yield most of their 10 hours -- starting the 10-hour timer for Democrats to debate passage overnight. Senate Majority Leader John Thune (R-S.D.) will be able to hold a final vote by early Monday morning.

If the Senate passes the bill, es expected after a successful cloture vote, it will go the House of Representatives, where the president and his legislative affairs team are actively engaged in courting Republican holdouts and critics to vote yes.