House Republicans are holding a markup of their impeachment articles against Department of Homeland Security Secretary Alejandro Mayorkas on Tuesday, moving closer to taking the rare step of impeaching a Cabinet official.

The House Homeland Security Committee will mark up its resolution claiming Mayorkas has committed high crimes and misdemeanors for his handling of the southern border, even though a number of constitutional experts have said the evidence does not reach that high bar.

The controversial move would make Mayorkas the first Cabinet secretary to be impeached in nearly 150 years.

The impeachment effort comes as House Republicans have faced building pressure from their base to hold the Biden administration accountable on a key campaign issue: the border.

While Republicans have been investigating Mayorkas’ handling of the border since they reclaimed the House majority, their impeachment inquiry has moved swiftly in the new year. House Speaker Mike Johnson has promised to move the articles of impeachment against Mayorkas to the floor quickly, and has signaled he will reject a bipartisan deal being negotiated in the Senate that would address border policies.

While senior House Republicans are confident they have the support to impeach the DHS secretary, they can lose only two votes given their narrow majority. Republicans are planning a whip check this week to take the temperature of the conference, a GOP source told CNN.

House GOP Whip Tom Emmer told CNN ahead of the markup that he is counting votes, but added: “We are going to have to pass that. I mean, it’s pretty egregious what he’s done.”

House Homeland Security Chairman Mark Green of Tennessee has been meeting with some of the remaining GOP holdouts, such as Rep. Ken Buck of Colorado, and has issued a number of memos on Mayorkas in recent weeks, according to GOP sources. Green presented his case to senior Republicans during a closed-door meeting Monday night, telling CNN afterward that “nobody had any questions or dissent.”

In a sign of growing momentum for the effort, GOP swing district Rep. Don Bacon said he will vote to impeach Mayorkas. But Washington Rep. Dan Newhouse, another moderate House Republican lawmaker, was less definitive.

“I want to hear all of the arguments for it. I understand that there is quite a groundswell of support for it, and I want to just understand it totally,” Newhouse said.

Ahead of the markup, Green outlined his case for why Mayorkas should be impeached.

“These articles lay out a clear, compelling, and irrefutable case for Secretary Alejandro Mayorkas’ impeachment,” Green said in a statement provided to CNN. “He has willfully and systemically refused to comply with immigration laws enacted by Congress. He has breached the public trust by knowingly making false statements to Congress and the American people, and obstructing congressional oversight of his department.”

Green argued Mayorkas’ “willful and systemic refusal to comply with the law” and “breach of public trust” amounts to the impeachable offenses of high crimes and misdemeanors. Green claimed Mayorkas has “willfully exceeded” his parole authority, “refused to comply” with detention mandates, and lied for saying that DHS has “operational control” over the border. He cited Supreme Court Justice Samuel Alito, who said Congress could “employ the weapons of inter-branch warfare,” including impeachment, in light of the Supreme Court ruling that states could not challenge federal immigration law.

But a variety of legal scholars have poured cold water on the legal arguments Republicans are using to support their impeachment effort.

Ross Garber, a Tulane law professor who has represented many Republican officeholders as both the prosecution and defense in impeachment cases, told CNN that House Republicans have not presented evidence of impeachable offenses.

“I think that what the House Republicans are asserting is that Secretary Mayorkas is guilty of maladministration,” Garber said. “At least as framed right now, the charges don’t rise to the level of a high crime or misdemeanor.”

Former DHS Secretary Michael Chertoff, who served under Republican President George W. Bush, wrote in a recent op-ed, “as a former federal judge, U.S. attorney and assistant attorney general — I can say with confidence that, for all the investigating that the House Committee on Homeland Security has done, they have failed to put forth evidence that meets the bar.”

Constitutional law expert Jonathan Turley, who has been called by Republicans to serve as a witness in hearings, said, “There is no current evidence he is corrupt or committed an impeachable offense,” and 25 law professors wrote in an open letter that impeaching Mayorkas would be “utterly unjustified as a matter of constitutional law.”

Despite outside voices, a growing number of House Republicans, including House GOP leadership, support impeaching Mayorkas.

Even if Mayorkas were impeached, it is highly unlikely that he will be charged in the Democratic-controlled Senate.

Mayorkas sent a letter to Green ahead of Tuesday’s markup, detailing how he came into a career in public service and defending his record.

“My reverence for law enforcement was instilled in me by my parents, who brought me to this country to escape the Communist takeover of Cuba and allow me the freedoms and opportunity that our democracy provides,” Mayorkas said.

Mayorkas wrote that “the problems with our broken and outdated immigration system are not new” and called on Congress to help provide a legislative solution to the “historically divisive issue.” He praised the bipartisan group of senators he has worked with for its willingness to put their differences aside to try to find solutions at the border.

The Department of Homeland Security has also blasted House Republicans over its upcoming committee vote, calling it a “farce” and “distraction from other vital national security priorities.”

In a memo, DHS slammed the impeachment inquiry, arguing that there are no high crimes or misdemeanors, that the probe was “predetermined from the start,” and that the process is “cynical and hypocritical.”

In response to Republicans blaming Mayorkas for the uptick in border crossings, the DHS memo states, “This Administration has removed, returned, or expelled more migrants in three years than the prior Administration did in four years.”

Addressing the claim that Mayorkas has failed to maintain operational control over the border, DHS said that based on the way the law defines operational control, “no administration has ever had operational control.”

Democrats on the Homeland Security Committee have repeatedly bashed their Republican colleagues for their efforts to impeach Mayorkas. Ahead of Tuesday’s markup, Democrats released a report calling the GOP effort “a sham.”

“What is glaringly missing from these articles is any real charge or even a shred of evidence of high crimes or misdemeanors – the Constitutional standard for impeachment,” Democratic Rep. Bennie Thompson, the top Democrat on the Homeland Security Committee, said in a statement in response to the Mayorkas impeachment articles.

Swift impeachment inquiry process

Momentum to plot a swift impeachment of the Cabinet secretary picked up steam this month as key swing-district Republicans expressed fresh openness to the idea amid a recent surge of migrant crossings at the southern border.

The focus on Mayorkas amounts to a shift for the House GOP, which had set its sights on potentially impeaching President Joe Biden in early 2024. But with the Biden probe moving methodically and a number of Republicans still skeptical about impeaching the president, senior Republicans now believe targeting Mayorkas will be an easier lift as the border crisis becomes a defining campaign issue.

Instead of formally launching an impeachment inquiry with a House floor vote, the effort has been unilaterally run through the Homeland Security Committee as opposed to the House Judiciary Committee, where impeachment articles typically originate, though it is not constitutionally required.

“When a committee chair doesn’t vote for regular order, it’s a huge disservice to the institution,” House Financial Services Chairman Patrick McHenry, a North Carolina Republican, said of how the Mayorkas impeachment process unfolded.

In the investigative phase, Homeland Security Committee Republicans held 10 hearings, published five interim reports, and conducted 11 transcribed interviews with current and former Border Patrol agents. But since launching the inquiry, the GOP-led panel has held only two hearings and has decided to move forward with impeachment articles without giving the secretary an opportunity to testify.

Republicans invited Mayorkas to testify at an impeachment hearing on January 18. But the DHS secretary said he was hosting Mexican Cabinet members to discuss border enforcement, and he asked to work with the committee on scheduling a different date, according to a letter obtained by CNN.

Green said his committee has given Mayorkas “chance after chance to appear,” but Mayorkas wrote that he has testified before Congress more than any other Biden Cabinet official, noting that seven of those times were in front of Green’s committee.

“Whatever proceedings you initiate, however baseless, my responsiveness to oversight requests will not waiver,” Mayorkas said.

This story has been updated with additional developments.

CNN’s Melanie Zanona and Priscillia Alvarez contributed to this report.