Kirstjen Nielsen will be remembered as a villain, but her departure does not mean Trump's immigration agenda will be any less extreme

Associated Press/Jacquelyn Martin

President Donald Trump listens as Homeland Security Secretary Kirstjen Nielsen speaks in the Rose Garden of the White House after a meeting with Congressional leaders on border security, Friday, Jan. 4, 2019, at the White House in Washington.

• Kirstjen Nielsen has resigned as chief of the Department of Homeland Security.
• Nielsen was wildly unpopular due to her association with the "zero tolerance" policy that saw thousands of migrant children separated from their families.
• Nielsen's tenure was chaotic and she was often the target of Trump's ire.
• Her exit signals that the Trump administration is taking its immigration agenda in a more extreme direction.
• Nielsen's resignation is just the latest in a long line of departures of cabinet secretaries and top officials from this administration.

Kirstjen Nielsen has been the face of President Donald Trump's hawkish immigration agenda since taking over the role as chief of the Department of Homeland Security (DHS) in December 2017.

Nielsen resigned as Trump's DHS secretary on Sunday after a tumultuous tenure and as the president continues to push for an end to undocumented immigration by virtually any means necessary. The president's critics will look back on Nielsen as a villain who separated thousands of migrant children from their families and put them in cages.

Read more: Hundreds of migrants are being detained under a bridge in El Paso amid a surge of families crossing the border. Border Patrol agents say there's nowhere else to put them.

Nielsen not only defended family separations, but also sought to deny the administration had ever enacted the policy.

The image of a terrified migrant mother holding her children's hands and running from tear gas fired by Border Patrol will likely forever be associated with Nielsen. She defended these tactics, as well.

Under Nielsen's watch, two migrant children died in Border Patrol custody, which she blamed on the families for making the dangerous trek and crossing illegally.

Kim Kyung-Hoon/Reuters

A migrant family, part of a caravan of thousands traveling from Central America en route to the United States, run away from tear gas in front of the border wall between the U.S and Mexico in Tijuana, Mexico November 25, 2018.

"She'll be remembered for enthusiastically promoting the most controversial policies and for the misinformation she pushed out regularly," Greg Siskind, and immigration attorney based out of Memphis, Tennessee, told INSIDER of Nielsen. "I can't think of one positive thing to say."

Echoing these views, Matthew Kolken, an immigration attorney in Buffalo, New York, told INSIDER, "[Nielsen] will be remembered as the face of child separations, one of darkest and unwashable stains on the history of our country. She was tasked with putting a smiling face on the policy of enforced cruelty. If I were her I wouldn't be able to sleep at night."

But Nielsen's departure does not signal an end to the White House's hardline approach to the border, and instead showcases Trump's dissatisfaction with her inability to successfully implement the more extreme aspects of his immigration agenda.

Siskind told INSIDER he's sure Trump is "hoping for someone more extreme" to replace Nielsen.

Mana Yegani, an immigration lawyer in Houston, Texas, told INSIDER the departing Homeland Security secretary "will not be remembered well."

"Kirstjen Nielsen will be remembered as putting children in cages. Not being accountable for the hundreds of children becoming orphans as they were separated from their parents," Yegani said. "She will be remembered for those parents who committed suicide because their babies were taken away from them."

"As President Trump ramps up for reelection he wants immigration to be front and center. He wants to say that he got rid of those who couldn't control the border and he is bringing on fresh new management to stop asylum seekers," Yegani added on why Nielsen has resigned.

For now, Kevin McAleenan, who's been serving as US Customs and Border Protection commissioner, will take over from Nielsen as acting DHS chief. McAleenan is a career official who also worked in the Obama administration, and does not seem to be the likely choice for a permanent replacement - especially given his views on immigration seem to be at odds with Trump's and his senior advisers like Stephen Miller.

Similarly, Democratic Rep. Ted Lieu on Sunday tweeted, "I would like to believe [Trump] fired [DHS] Secretary Kirstjen Nielsen because she separated toddlers and children from their parents, and also put people in cages. But I fear [Trump] fired her because she wasn't cruel enough."

Nielsen and Trump's relationship was fraught from the earliest days of her role as DHS chief, but became particularly strained more recently over her apparent failure to block asylum seekers from entering the country.

"The asylum program is a scam. Some of the roughest people you've ever seen - people that look like they should be fighting for the UFC - they read a little page given by lawyers that are all over the place. They tell them what to say," Trump said in Las Vegas on Saturday.

Trump in recent weeks has also made bold, vague threats to close the border if Mexico didn't find a way to stop illegal crossings amid in a surge in attempts from migrant families primarily emanating from Central American countries like El Salvador, Guatemala, and Honduras. Some experts have suggested Trump's "zero tolerance" policy has induced the surge, contending it inadvertently highlighted legal protections for migrants in the US and inspired more to attempt the journey.

Read more: Trump mocks asylum-seekers at the border, says they 'look like they should be fighting for the UFC'

"I hope that the next Secretary will have the support of Congress and the courts in fixing the laws which have impeded our ability to fully secure America's borders and which have contributed to discord in our nation's discourse," Nielsen said in her resignation letter, echoing calls she's made in recent weeks for lawmakers to implement more iron-fisted immigration laws.

When Trump on Friday announced he's withdrawing his nomination of Ron Vitiello to head US Immigration and Customs Enforcement (ICE), he told reporters he wanted someone who would take the immigration agency in a "tougher direction."

Meanwhile, Trump has reportedly been calling on his administration to reinstate the "zero tolerance" family separation policy he ended via an executive order in June. Nielsen pushed against this, according to NBC News, which increased tensions between her and the president.

Earlier this year, despite bipartisan opposition in Congress, Trump also declared a national emergency to obtain funding for a border wall. More recently, he cut aid to Central American countries as punishment for the flow of migrants.

Trump's rage over undocumented immigration has seemingly reached new heights in 2019. After Nielsen's resignation was announced on Sunday, he tweeted, "Mexico must apprehend all illegals and not let them make the long march up to the United States, or we will have no other choice than to Close the Border and/or institute Tariffs. Our Country is FULL!"

Many of Nielsen's harshest critics are celebrating her departure, but all of the signs suggest Trump is poised to replace her with someone they'll despise even more.