An amendment named after slain Augusta University 22-year-old nursing student Laken Riley from Georgia is at the center of a Senate showdown over the $1.2 trillion spending package that must pass before midnight to avoid a partial government shutdown.

The Laken Riley Act has been introduced as an amendment to the six-bill appropriations package by Sen. Ted Budd, R-N.C., but sources have told Fox News Digital that Democrats are unwilling to agree to a vote on it.

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His modified Laken Riley Act would stop illegal immigrants from gaining citizenship or legal status if they've ever committed burglary, theft, or shoplifting.

Budd's second proposed amendment to the spending bills is also immigration-related, and also being contested in negotiations. The amendment would similarly prevent illegal immigrants from becoming legal or citizens if they've assaulted a law enforcement officer.

Laken Riley’s killing has gripped the nation as the border crisis continues. (ELIJAH NOUVELAGE/AFP via Getty Images)

Budd said in an exclusive statement to Fox News Digital, "We know that the Biden administration would love nothing more than to grant legal status to illegal aliens who are unlawfully living in this country. So I am fighting to defund the ability of the Biden administration to grant any sort of legal status to any illegal alien who commits crimes like assaulting a law enforcement officer; as well as theft and shoplifting."

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Three GOP Senate sources told Fox News Digital that a specific obstacle to consideration of the immigration-related amendments is Sen. Jon Tester, D-Mont., who frequently postures himself as a moderate and is up for re-election in a competitive match-up in November. The sources detailed he is particularly against being on record on the Laken Riley Act.

Sen. Jon Tester, D-Mont. (Drew Angerer)

Sen. Tommy Tuberville, R-Ala., called Tester out by name on X, formerly known by Twitter, on Friday night.

"Tonight, @TheDemocrats are shutting down the United States government because they don't want @jontester to have to vote against OPEN BORDERS in an election year. I can't wait for @SheehyforMT to send him packing. #MAGA," he wrote.

Republican Minority Whip John Thune similarly blamed Democrats for the nearly inevitable shutdown. "Make no mistake, if the government shuts down, it will be because of one thing and one thing only: Democrat leaders protecting vulnerable incumbents from taking hard votes," he said on X.

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However, Tester is pushing back on the idea. "This is false and Senator Tester is happy to debate amendments. He is pushing his colleagues to hire more border patrol agents, secure our border, and crack down on fentanyl," spokesperson Eli Cousin told Fox News Digital in a statement.

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But the immigration amendments aren't the only hang-up in the Senate's negotiations to bring the spending package to the floor for a vote. According to two senior Republican Senate sources, Majority Leader Chuck Schumer, D-N.Y., refuses to allow a vote on any amendments that are "germane" or might pass with bipartisan support.

Senate Majority Leader Charles Schumer, D-N.Y. (Tom Williams/CQ-Roll Call, Inc via Getty Images)

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"Anything that can pass would send the bill back to the House," a source in Schumer's office shared with Fox News Digital.

If any amendments to the spending package are passed, the bills would head back to the House to be voted on again. This would ultimately trigger a partial shutdown, which the Senate negotiators were hoping to avoid.