As President Biden reaches the 100-day mark in office, one of the biggest issues facing his administration has been the rapidly worsening crisis at the southern border -- which critics have blamed on his dramatic rollback of Trump-era policies which started on day one.

Biden had made the turning back of former President Donald Trump’s immigration policies one of the key planks in his 2020 presidential campaign. And on day one, he got straight to work.

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Day One

Biden signed orders immediately after his inauguration that halted construction of the wall at the southern border, committed to strengthening the Deferred Action for Childhood Arrivals (DACA) program and repealed the travel bans on high-risk countries from the Middle East, Africa, as well as Venezuela and North Korea.

His administration also touted his support for a sweeping immigration reform bill that would include a pathway to citizenship for millions of illegal immigrants.

Meanwhile, the Department of Homeland Security issued a memo with guidance that dramatically narrowed interior immigration enforcement to recent border crossers, national security threats and "aggravated felons." That guidance also sought to impose a 100-day moratorium on deportations.

Remain-in-Mexico

In the subsequent weeks and months, Biden made a number of key moves on immigration. Most critically he ended the Migrant Protection Protocols (MPP). That policy, known as the "Remain-in-Mexico" policy, was a Trump-era policy that kept migrants in Mexico while their hearings proceeded. Proponents said it ended the pull factor of allowing migrants into the interior, while critics called it a cruel policy that put migrants in danger.

The Biden administration also did not apply Title 42 public health restrictions -- which allowed the US to quickly expel migrants -- to unaccompanied children and some family units.

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Border crisis escalates

The number of migrant encounters at the border had been steadily increasing since April 2020 and continued as the COVID-19 pandemic escalated. But Trump officials and Republicans warned during the transition that, if Biden rolled back Trump-era policies, there would be chaos.

"If the current policies in place are revoked as critics have promised they would do...the 2,300 [encounters] a day will become a full-blown crisis overnight as we stand by and watch the numbers go even higher, making last year's crisis pale in comparison," then-acting Customs and Border Protection Commissioner Mark Morgan said in December.

There seemed too to be some indication to Biden officials that new trouble was ahead, with top advisers warning potential migrants that the border would not be open right away.

As Biden entered office, numbers surged and continued to grow in the weeks ahead. There were more than 100,000 migrant encounters in February, and more than 172,000 encounters in March -- with historic highs of unaccompanied children.

Meanwhile ICE enforcement narrowed significantly, and while the 100 day moratorium was blocked after a lawsuit from Texas, arrests plunged.

Soon, pictures of packed migrant facilities in places like Donna, Texas, emerged as officials quickly opened new facilities while ending some COVID-related capacity restrictions to cope with the influx. Elsewhere, videos were released of smugglers abandoning children in the wilderness. The administration put out appeals across the federal government for volunteers, while overwhelmed Border Officials started releasing migrants into the U.S. without notices to appear in court.

Critics quickly chalked the escalating disaster up to Biden’s changes to immigration policy. The administration denied there was a crisis at the border, calling it a "challenge" instead and blaming the Trump administration for ending legal asylum pathways and dismissing the surge as seasonal.

In March, Biden put Vice President Kamala Harris in charge, but the White House soon clarified that Harris was dealing not with the border itself, but with "root causes" of the crisis in Central America -- with her role involving speaking with leaders of Mexico and Northern Triangle countries to solve issues like poverty, violence and climate.

So far, there have been some agreements to strengthen border security at those country’s border, while Harris will visit Guatemala in June.

Doubling Down

But despite the crisis at the border, the Biden administration shows little sign of having changed its trajectory on migration. Biden has continued to push for immigration reform, including amnesties for illegal immigrants. On interior enforcement, he has picked an ICE nominee who has opposed ICE raids in the past.

However, Biden is likely to face continued heat from the left of the Democratic Party for not having completely ended Title 42 -- which is still being applied to some migrant families and single adults, and is responsible for the vast majority of migrants encountered at the border being returned.

Meanwhile, Biden continues to poll poorly on the issue, despite a number of high marks elsewhere.

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By a stark 46-15% margin, voters say U.S. border security is worse today than it was two years ago, according to the latest Fox News survey

By an 18-point margin, more disapprove (52%) than approve (34%) of Biden's performance on immigration. Views are nearly identical on border security, as just over half disapprove (51% vs. 35% approve).