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Alejandro Mayorkas, secretary of the US Department of Homeland Security, during a news conference while visiting the US-Mexico border in Eagle Pass, Texas, on Monday.

The House Homeland Security Committee on Wednesday held its first impeachment hearing focused on Secretary of Homeland Security Alejandro Mayorkas as Republicans push to impeach the top Biden administration official over the border crisis.

Republicans lambasted Mayorkas during the hearing over what they claim is a dereliction of duty as border crossings have reached record highs, while Democrats argued that the impeachment proceedings are politically motivated and meritless.

The hearing comes as the House GOP majority ramps up its scrutiny of the administration on multiple fronts. House Republicans continue to pursue an impeachment inquiry into President Joe Biden and are taking steps this week toward holding the president’s son Hunter Biden in contempt of Congress. 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.

If the Homeland Security secretary is impeached, it would be an exceedingly rare event. Only one Cabinet official has ever been impeached in American history - Secretary of War William Belknap in 1876.

The panel is expected to hold additional impeachment hearings as part of the proceedings against Mayorkas in addition to Wednesday’s initial hearing.

Once the hearings conclude, the panel is expected to hold a markup on articles of impeachment followed by a committee vote, which would set the stage for the articles to then be sent back to the full House for consideration.

The Constitution sets the standard for impeachment as treason, bribery, or “high crimes and misdemeanors.” Legal experts and conservative scholars have argued that policy disputes don’t rise to the level of high crimes and misdemeanors.

Chairman Mark Green, a Republican from Tennessee, argued during the hearing that impeachment does not have to be limited to limited to criminal behavior, but can also be a way to remove officials guilty of “gross incompetence.”

“The constitutional history is overwhelmingly clear on this subject — the founders designed impeachment not just to remove officials engaged in criminal behavior, but those guilty of such gross incompetence that their conduct had endangered their fellow Americans, betrayed the public trust, or represented a neglect of duty,” Green said.

“Secretary Mayorkas has brazenly refused to enforce the laws passed by Congress and has enacted policies that knowingly make our country less safe. What we’re seeing here is a willful violation of his oath of office taken by Secretary Mayorkas,” he said.

Many Democrats acknowledge the current immigration system is broken and the border has been overwhelmed – in part because global migration overall has increased – but they also strongly refute the notion that the border is “open” or that Mayorkas has violated any laws.

Rep. Bennie Thompson of Mississippi, the top Democrat on the panel, called the impeachment proceedings against Mayorkas “baseless.”

“It’s now campaign season, and Republicans recently rolled out their impeachment proceedings against the secretary like the pre-planned, pre-determined political stunt it is,” he said. “This is not a legitimate impeachment.”

One of the witnesses, Frank Bowman, a professor emeritus of law at the University of Missouri School of Law, was invited to testify by Democrats on the panel.

“If members of this committee disapprove of the Biden administration’s immigration and border policies, the Constitution gives this Congress a wealth of legislative powers to change them – impeachment is not one of those powers,” Bowman said.

Later, when asked by a Democratic lawmaker if he has seen any evidence that Mayorkas has taken action that reaches the Constitutional threshold for impeachment, Bowman said, “I’ve seen lots of reports about arguments about policy. I’ve seen nothing that rises to the level of an impeachable offense.”

The hearing also featured testimony from attorneys general from Montana, Oklahoma and Missouri – all Republicans – who called for stricter border security and outlined the consequences of the border crisis in their states, citing issues like the dire impact on communities of drugs trafficked across the border such as fentanyl.

“The southern border certainly presents a difficult challenge for any administration, but Secretary Mayorkas and the Biden administration have absolutely poured gasoline on this fire,” Montana Attorney General Austin Knudsen said.

DHS released a new memo Wednesday morning ahead of the hearing calling the impeachment push a “baseless political attack.” The memo states that the majority of all southwest border migrant encounters under the Biden administration have been removed, returned or expelled and DHS has stopped more fentanyl and arrested more individuals for fentanyl-related crimes in the past two years than the previous five years combined.

Mayorkas has pushed back against criticism and officials who work closely with him say he intends to remain in the post.

“Some have accused DHS of not enforcing our nation’s laws. This could not be further from the truth. Having begun my public service career as a federal prosecutor for 12 years, ultimately serving as the United States Attorney, there is nothing I take more seriously than our responsibility to uphold the law, and the men and women of DHS are working around the clock to do so,” Mayorkas said in remarks in Eagle Pass, Texas — the epicenter of the border crisis last month — on Monday.

Border authorities have encountered around 3,000 migrants crossing the US southern border daily this month, according to a Homeland Security official.

It’s a steep drop from December when daily encounters soared to more than 10,000 people. The official cited Mexico’s actions to move migrants along the country’s northern border further south and deporting Venezuelans for driving down the numbers.

White House officials have credited high-level talks with Mexico for the recent drop in border crossings. A delegation from Mexico is expected to visit Washington this month to continue those discussions.

“This extreme impeachment push is a harmful distraction from our critical national security priorities,” a DHS spokesperson said in a statement.

The hearing comes after the House voted in November to refer a resolution to impeach Mayorkas to the committee.

House faces jam-packed agenda in addition to Mayorkas impeachment push

The Mayorkas impeachment push adds another item to an already jam-packed congressional calendar in the new year. Lawmakers are facing two upcoming government shutdown deadlines and Senate negotiators are hoping to reach a deal on border policy, but the House and Senate are on a collision course over immigration.

A bipartisan group of senators has been in talks to try to strike a deal over border security that could clear the way for passage of aid for Ukraine and Israel – talks that Mayorkas has participated in. GOP Sen. James Lankford of Oklahoma has said that Mayorkas is not writing policy, but rather providing “technical assistance” as senators negotiate.

A growing number of House Republicans have warned, however, that a Senate compromise over border security stands virtually no chance of passing their chamber, making clear instead they will only accept a deal that mirrors the hardline immigration bill they passed last year – known as HR 2 – even though Senate Democrats and the White House strongly oppose that plan and call it a nonstarter.

House Republican demands over border security are also threatening to put the effort to avert a shutdown at risk as some conservatives have begun calling to shut down the government if their demands aren’t met.

Ian Sams, a White House spokesperson for oversight and investigations, said in a statement, “House Republicans are less than ten days from sparking a partial government shutdown that many of their far-right members are rooting for, but instead of working full-time to avoid it, they are wasting time on political stunts. These baseless attacks on the President’s Cabinet and family members will do nothing to help improve Americans’ daily lives, strengthen our border security, or improve the economy.”

In a sign of growing momentum for the drive to impeach Mayorkas, the effort has gained traction with key swing-district Republicans. But the House GOP majority is extremely narrow and some House Republicans have expressed skepticism over the push.

Jonathan Turley, a conservative law professor who was a witness at a House Oversight Committee hearing last fall on the potential impeachment of President Biden, wrote an op-ed in the Daily Beast on Tuesday arguing that Mayorkas has not committed any impeachable offenses, though he was highly critical of the secretary.

“In my view, Biden has been dead wrong on immigration, but voters will soon have an opportunity to render a judgment on those policies in the election. Mayorkas has carried out those policies. What has not been shown is conduct by the secretary that could be viewed as criminal or impeachable,” the op-ed states.

DHS pushing back ‘aggressively’ on impeachment push

The Department of Homeland Security has been plotting its response to impeachment proceedings against Mayorkas, who emerged as a top target of Republicans over the Biden administration’s border policies early on.

The department is planning to push back “aggressively,” according to a Homeland Security official, who described the attacks against the secretary and the department as “meritless.”

Over the course of the proceedings, Homeland Security officials plan to use a similar strategy to the White House in highlighting split-screen moments, like casting the House majority’s proceedings as a waste of time while Mayorkas has been working with senators to strike a border deal.

The department, according to the Homeland Security official, will focus on areas like the “unserious nature” of the investigation, attacks on border security efforts and lack of grounds or evidence for impeachment.

Senior communications, legal and legislative aides at the White House have been meeting regularly for weeks with senior DHS leadership to align on strategy, according to a source familiar, including in direct calls between Mayorkas and several of Biden’s aides.

The department has also hired a private law firm to help with impeachment proceedings. While the Department of Homeland Security Office of General Counsel has various lawyers to deal with matters, including immigration and cybersecurity, the outside firm was brought in on a government contract to be utilized to the extent needed throughout the process.

CNN’s Melanie Zanona and Lauren Fox contributed to this report.

This story and headline have been updated with additional developments.