Senate Republicans on Wednesday rejected a bipartisan measure negotiated by one of their own members aimed at bolstering security at the U.S.-Mexico border and providing aid to Israel and Ukraine.

After the bill failed, which was expected after GOP backlash one day prior, Senate Democrats moved forward with their backup plan: A standalone aid package for Ukraine, Israel and Taiwan without the border measures included.

But the process stalled as lawmakers in both parties sought to move forward.

The procedural motion failed in a 49-50 vote, falling short of the 60 votes needed to advance. Oklahoma Republican Sen. James Lankford, one of the key negotiators on the bipartisan border measure, supported it. In a stunning moment during the debate on the bill, Lankford said that he was threatened by a "popular commentator" for negotiating the bill.

"I had a popular commentator four weeks ago that I talked to that told me flat out, before they knew any of the contents of the bill ... that told me flat out 'if you try to move a bill that solves the border crisis during this presidential year, I will do whatever I can to destroy you,'" Lankford said. "Because I do not want you to solve this during the presidential election."

"By the way, they have been faithful to their promise, and have done everyhthing they can do destroy me in the past several weeks," the Oklahoma Republican added.

In a passionate speech on the Senate floor ahead of the vote, Arizona Sen. Kyrsten Sinema, lamented the loss of the bill's border provisions and condemned Republican lawmakers who opposed the bill while campaigning on securing the U.S.-Mexico border.

"Less than 24 hours after we released the bill, my Republican colleagues changed their minds," Sinema, an independent, said. "Turns out they want all talk and no action. It turns out border security is not actually a risk to our nat. security, it’s just a talking point for the election.”

“After all those trips to the desert, after all those press conferences, it turns out this crisis isn’t much of a crisis after all," she said, later adding: "So if you want to spend the border crisis for your own political agendas, go right ahead, but I have a very clear message for anyone using the southern border for staged political events: Don't come to Arizona. Take your political theater to Texas."

"Partisanship won," she added. "The Senate has failed Arizona. Shameful."

Sinema and fellow negotiator Connecticut Sen. Chris Murphy, a Democrat, both joined Lankford in supporting the measure. After the failed vote, Murphy called the negotiation process "the most outrageous thing that I have been a part of in my 16 years in Congress."

Schumer thanked Sinema for her "strong, courageous and heartfelt words" after her speech, saying that Senators "have a chance to show precisely where they stand" on border security with their procedural vote on the initial border security and international aid measure.

"The choice is plain and simple, and this vote will show precisely who is serious about securing the border and who is not," he added. "I hope our Republican colleagues, so many of whom know this is the right thing to do, will not bend to the wishes of Donald Trump, who only wants chaos."

Following the failed vote, lawmakers moved ahead with considering the standalone aid bill -- though a procedural vote on the measure was held open for hours as they tried to find consensus on a way forward. The Senate eventually adjourned until Thursday afternoon "to give our Republican colleagues the night to figure themselves out," Schumer said.

Republicans were deeply divided during a closed-door luncheon as they debated how to proceed on the funding package, according to those in the meeting. And the Senate settled into an hours-long standstill as senators negotiated amendments for the standalone package.

The new bill comes in at just north of $95 billion -- less than the original bill and the $106 billion initially requested by President Joe Biden last year -- and would provide $60 billion in aid for Ukraine as it repels Russia's invasion, $14 billion for Israel for its fight against Hamas, nearly $2.5 billion to support U.S. Central Command operations in the Middle East and $4.83 billion in aid for Indo-Pacific allies, including Taiwan, to counter China's influence in the region. It also includes more than $9 billion in humanitarian aid for civilians in Gaza, the West Bank and Ukraine and the FEND Off Fentanyl Act, which authorizes sanctions against entities engaged in trafficking the deadly substance.

It comes after Senate Republicans declared the initial bill all but dead at a press conference on Tuesday, just after President Biden urged GOP members of Congress to reconsider. Leader McConnell said that "we have no real chance here to make a law" amid concerns from within his own conference as well as the opposition of House Republicans, whose leader, Speaker Mike Johnson, R-La., repeatedly declared the bill "dead on arrival" in the lower chamber.

But the Kentucky Republican did signal that his conference could support a bill to provide international aid without the border provisions, despite the fact that members of the GOP had initially demanded that any additional support to Ukraine be linked to immigration reform. McConnell said that "there are other parts" of the bill that are "extremely important," urging lawmakers to pass aid to Israel, Ukraine and Taiwan and saying it's on Schumer to "repackage" the bill to reflect that.

Schumer told reporters on Wednesday that he communicated to the White House and his Senate Democratic conference that he planned to hold a vote to advance the aid bill, sans border provisions, immediately after the procedural vote on the border bill failed. A Senate Democratic aide told Spectrum News that the move could force Republicans to vote down the bill twice in one day, per the aide, which they called an “embarrassing prospect.”

"First Republicans said they would only do Ukraine and Israel and humanitarian aid with border, then they said they would not do it with border," he said earlier Wednesday. "Well, we're gonna give them both options." 

"We'll take either one," he continued. "We just hope they can come to 'yes' on something."

Even if the bill passes the Senate, it could set up a collision with House Republicans -- though things could be different after the lower chamber scuttled a $17 billion standalone Israel aid bill on Tuesday evening.

When asked if he believes the House will take up the bill, Schumer said that he hopes the lower chamber "would rise to the occasion" should the measure pass the Senate.

"The House is in chaos," he said. "It doesn't behoove the speaker well to block everything because 30 hard right-wing people just want chaos like Donald Trump.”

The measure could also face some resistance from the left flank. Progressive Vermont Sen. Bernie Sanders voted against it, citing an unwillingness to provide additional funding to Israeli Prime Minister Benjamin Netanyahu's government.

"This bill provides $10 billion more in U.S. military aid for the Netanyahu government to continue its horrific war against the Palestinian people," Sanders said in a statement ahead of the vote. "That is unconscionable. I will be voting NO."

Timing could also be a concern, with the Senate about to embark on a two-week recess starting this weekend. 

Schumer said that he "knew" a fallback option might be necessary after former President Trump started coming out against the border bill, and that this bill will contain everything the original bill had, sans the immigration positions -- though measures to address the scourge of fentanyl, which is somewhat related to border security, are included, he noted.

"We just hope they can come to 'yes,'" Schumer said of his Republican colleagues. "We will have the second vote if the first vote fails. I still hope that they would rethink the first vote. Donald Trump wants chaos. Donald Trump does not want success at the border, he wants chaos, and if he became president I doubt he'd ever solve it."

"We want them to pass the border bill," he continued, before echoing President Biden's comments from Tuesday: "If they vote against the bill, America will know who is for fixing the border and who is not."

The Associated Press contributed to this report.