WASHINGTON (AP) — The House of Representatives is expected to vote Tuesday on whether to impeach Homeland Security Secretary Alejandro Mayorkas. It’s not clear whether Republicans have the votes to impeach but if they do it would mark the first time in nearly 150 years that a Cabinet secretary has been impeached.

The vote will be the culmination of months of examination by House Republicans as they’ve aimed to make immigration and border security a key election issue.

Here’s a look at how the House arrived at the impeachment vote and where things go from here:

WHAT’S GOING ON AT THE BORDER?

READ MORE House Republicans are ready to impeach Homeland Security Secretary Mayorkas. Vote will be close Mayorkas is driven by his own understanding of the immigrant experience. Many in GOP want him gone Mayorkas is driven by his own understanding of the immigrant experience. Many in GOP want him gone

Migrants have long come across the southern U.S. border looking for a new life in the United States, but not like what’s happening now. Arrests for illegal border crossings from Mexico reached an all-time high in December. In fiscal year 2022, Border Patrol encountered 2.2 million people crossing the border illegally. You have to go back decades to see comparable numbers.

Statistics aren’t always a perfect measure though. The numbers from the 1990s and 2000s are considered vast undercounts because migrants sought to evade authorities as they entered the U.S.

Decades ago, the typical migrant trying to come to the U.S. was a man from Mexico looking for work, and he tried to dodge Border Patrol agents. That dynamic has changed drastically. Migrants now are still coming from central and south America but they’re also coming from much farther away — China, Afghanistan and Mauritania, to name just a few countries. And they’re often seeking out Border Patrol agents in an effort to seek protection in America.

The numbers have at times overwhelmed the ability of border officials to handle, leading to temporary closures of border crossings so that officials can process migrants.

It’s also had repercussions far from the border. Migrants going to cities like Chicago, New York, Boston and Denver have strained city services, leading to Democratic officials pushing the administration to take action.

WHAT DO REPUBLICANS SAY?

Republicans have laid the blame for all of this on the Homeland Security secretary and said that because of it, he needs to go. They say the Biden administration has either gotten rid of policies that were in place under the Trump administration that were deterring migrants or that the Biden administration implemented policies of its own that have attracted migrants.

The House Homeland Security Committee has been holding hearings over roughly the last year where Republicans have repeatedly lambasted Mayorkas. Witnesses have included an Arizona sheriff, families who have lost loved ones to the fentanyl crisis, experts on constitutional law, and former Homeland Security officials who served under Trump.

U.S. House Republicans say the secretary is violating immigration laws by not detaining enough migrants and by implementing a humanitarian parole program that they say bypasses Congress to allow people into the country who wouldn’t otherwise qualify to enter. And they allege that he’s lied to Congress when he’s said things like the border is secure. All of this together, they argue, has created a prolonged crisis that is having repercussions across the country, is squarely the secretary’s fault and warrants impeachment.

“There is no other measure for Congress to take but this one,” House Speaker Mike Johnson, a Republican from Louisiana, said Tuesday. “It’s an extreme measure, but extreme times call for extreme measures.”

WHAT DO MAYORKAS, HIS SUPPORTERS AND OTHERS SAY?

Democrats and many legal experts have said that this is essentially a policy dispute and that Republicans just don’t like the immigration policies that the Biden administration via Mayorkas has implemented. That’s an issue for voters to decide, not an issue that meets the level of “high crimes and misdemeanors” required to impeach a Cabinet official, they argue.

“That one congressional party disapproves, even disapproves vigorously, of President Biden’s policies on immigration or other matters within the secretary’s purview does not make the secretary impeachable,” testified University of Missouri law professor Frank O. Bowman during a January committee hearing.

Secretary Mayorkas and supporters have often said that it’s not the actions of the administration that are drawing migrants to the southern border, but that it is part of a worldwide phenomenon of migrants, driven by political, economic and climate turmoil, who more willing to embark on life-threatening journeys to seek out a better life.

They argue the administration has tried to deal with the chaos at the border. Over roughly the last year, Mayorkas has been the public face of a policy that seeks to create pathways for migrants to come to the U.S. such as an app that lets them schedule a time to come to the border and seek entry. And, they argue, that policy has new efforts to limit who can get asylum and to order aggressive deportations.

But the Biden administration and supporters contend that the secretary is dealing with a wildly underfunded and outdated immigration system that only Congress has the power to truly fix. So far, they argue, it hasn’t.

WHAT HAPPENS IF MAYORKAS IS IMPEACHED?

He still has a job. Once someone is impeached, the issue goes to the Senate. That’s the body that would decide whether to convict the secretary or not and if he’s convicted then Mayorkas is no longer Homeland Security secretary.

But conviction is a much higher bar than impeachment. Democrats control the senate 51-49. Two thirds of the Senate must vote to convict as opposed to the simple majority needed to impeach in the House. That means all Republicans as well as a substantial number of Democrats would have to vote to convict Mayorkas — a highly unlikely scenario considering some Republicans are cool to the idea of impeachment.

Mayorkas has said he’s ready to defend himself in the Senate if it comes to a trial. And in the meantime, he says he’s doing his job.

“I am totally focused on the work and what we need to get done. And I am not distracted by the politics,” Mayorkas said during a recent interview with The Associated Press.