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WASHINGTON — A showdown is coming between President Trump and Congress over arms sales to Saudi Arabia.

A bipartisan group in the Senate — including some of Trump’s top allies — are planning a vote this summer to block the sale of $8 billion in American weaponry to a regime implicated in the death and dismemberment of Washington Post writer Jamal Khashoggi, as well as using those weapons to commit atrocities in Yemen.

The Senate coalition ranges from progressives to libertarians who are outraged that top administration officials are claiming there’s an emergency in the Middle East that warrants them making those sales without approval of Congress.

“I think there’s a growing number of people and a growing resistance to allowing the government to operate by emergency,” Sen. Rand Paul (R-Ky.) told VICE News while rushing through the underbelly of the Capitol on the way to cast a vote. “So I think that you’re going to see the biggest vote we’ve had.”

It won’t be the first time Congress has tried to force a historic vote on the War Powers Act. In March, both the House and the Senate voted to end U.S. involvement in the war in Yemen, but Trump vetoed the measure.

This time, lawmakers are planning to force individual votes on all 22 of the arms sales already approved by the administration. And even Trump’s normally reliable Senate allies are preparing to confront the Trump administration on the Senate floor because they see the arms sales as an executive power grab.

Executive power grab

“Clearly I disagree with it,” Sen. Lindsey Graham (R-S.C.), who chairs the Judiciary Committee and is a lead sponsor of this effort, told VICE News on his way to a bank of elevators at the Capitol.

Foreign arms sales are supposed to go through Congress, but at the end of last month Secretary of State Mike Pompeo claimed Iran posed a big enough threat to American interests that he declared an emergency in order to go around Congress.

“It’s a moment of confrontation with the administration over fundamental foreign policy in this country”

But senators in both parties aren’t buying that line — even after they were given classified briefings on Iran last month.

“I really think it’s a moment of confrontation with the administration over fundamental foreign policy in this country,” Senate Minority Whip Dick Durbin (D-Ill.) told VICE News.

While Saudi Arabia has been a top American ally for decades, Crown Prince Mohammed bin Salman (or MBS) lost the faith of many senators after the American intelligence community found he'd helped orchestrate the torture and killing of Khashoggi last October.

Trump has rejected those findings even after the CIA concluded top Saudi officials not only condoned but ordered the operation.

Nuke technology

This week Sen. Tim Kaine (D-Va.) revealed the Department of Energy has been helping Saudi Arabia attain highly sensitive nuclear information — at least twice since the dismemberment of Khashoggi, which the agency has confirmed. And that information is raising red flags on its own, according to Kaine.

“I’m worried about our people getting these approvals — these business-as-usual approvals — to transfer nuclear technology to the Saudis because they’re close to the Trump family,” Kaine told VICE News. “It’s not business as usual. It’s business as un-usual with the Saudis, and we need to understand why.”

While Kaine’s revelation is slowly getting out to the Senate, and angering his colleagues in both parties along the way, there was already momentum building to rebuke the Trump administration for attempting to conduct arms sales without approval from Congress.

“Even though I may support the actual sale of defensive weaponry, I don’t support the administration going around the existing congressional review process,” Sen. Marco Rubio (R-Fla.) told reporters on his way to vote. “I don’t believe the administration should be able to go around what Congress has always done.”

Rubio says he still needs to review the exact language of the 22 resolutions to disapprove of the arms sales, but his gut is leaning toward rejecting Trump’s latest attempt to circumvent Congress.

That’s what’s brought about this strange bipartisan mix of lawmakers who are ready to rebuke Trump and his top officials for what they say is playing fast and loose with the constitutional separation of powers.

People on both sides of the political divide don't get why the president wouldn’t just ask for congressional approval for arms sales, like most of his presidential predecessors have done.

“This is so unnecessary,” Sen. Chris Murphy (D-Conn.) told VICE News at the Capitol. “He might actually end up getting the sale rejected by doing it this way.”