The number of migrants crossing into the U.S. illegally at the southern border reached the lowest point of President Biden’s administration in September, three months into his crackdown on asylum claims, according to internal Department of Homeland Security statistics obtained by CBS News.

In September, U.S. Border Patrol agents recorded nearly 54,000 apprehensions of migrants who crossed into the country between legal entry points along the border with Mexico, the government figures show. It’s a smaller figure than the previous Biden-era low in July, when Border Patrol processed roughly 56,000 migrants who crossed the border without authorization. 

Border Patrol’s tally of migrant apprehensions in September is the lowest number recorded by the agency since August 2020, when the Covid-19 pandemic and the travel restrictions countries enacted in response to it led to a sharp decrease in migration to the U.S. southern border. It’s also a 78% drop from a record high in December, when illegal border crossings soared to 250,000.

U.S. immigration officials processed another 48,000 migrants in September at legal border entry points, known as ports of entry, according to the internal federal data. Most of them secured appointments to enter the U.S. via a phone app the Biden administration has transformed into the main gateway into the American asylum system.

September’s numbers show migration to the U.S.-Mexico border has plateaued following a precipitous drop at the start of the summer, when President Biden invoked sweeping presidential powers to disqualify most of those entering the country illegally from asylum. In July, August and September, Border Patrol agents at the southern border recorded between 54,000 and 58,000 migrant apprehensions each month. 

Designed to be temporary, Mr. Biden’s move to sharply restrict asylum is likely to remain in place indefinitely after his administration made the policy’s deactivation threshold harder to meet last week. Vice President Kamala Harris has also vowed to continue the strict measure if elected president and make it even more difficult to lift. 

The Biden administration’s support for drastic limits on asylum reflect a broader rightward shift on border policy by Democrats that would have been unthinkable in 2020, when the party faced pressure to reverse the Trump administration’s hardline immigration rules. It’s a shift that has occurred amid a marked increase in support for tough immigration measures among the American public.

The dramatic reduction in illegal border crossings this year, however, has given Democrats a much-needed political win on immigration ahead of the presidential election next month. Former President Donald Trump, who is pledging to carry out mass deportations if voters return him to the White House, has sought to make immigration a defining issue of the 2024 race for the president.

With September’s tally, fiscal year 2024 saw the lowest level in unlawful border crossings under the Biden administration. Border Patrol recorded over 1.5 million migrant apprehensions in fiscal year 2024, compared to a record high of 2.2 million in fiscal year 2022.

While the Mexican government’s efforts have also played a major role in the lower number of migrant arrivals along the U.S. border this year, American officials have credited Mr. Biden’s stringent asylum rules in June for the current four-year low in illegal immigration levels.

During its first three years in office, the Biden administration struggled to respond to an unprecedented migrant influx that was, in great part, fueled by arrivals from far-flung countries, including nations like Venezuela where the U.S. cannot deport migrants on a regular basis due to frosty diplomatic relations. In many cases, migrants were released into the U.S. with notices to appear in immigration court simply because the government did not have the resources and personnel to vet their asylum claims at the border.  

But since Mr. Biden’s partial ban on asylum claims took effect, there has been an 80% drop in migrant releases, a senior Customs and Border Protection official told CBS News, requesting anonymity to speak candidly about migration trends. The U.S. government has long viewed migrant releases as a “pull” factor that fuels migration to the southern border, alongside economic conditions and other “push” factors in migrants’ home countries.

More than 70% of migrant adults and families apprehended by Border Patrol have been deported from the U.S. since Mr. Biden’s asylum crackdown began, up from 25% in May, according to DHS data. Since the policy took effect, the U.S. has carried out over 121,000 returns and deportations of migrants.

The asylum restrictions do not apply to unaccompanied children or those with acute medical conditions. It also exempts more than 1,000 migrants who enter the U.S. at legal border entry points each day under the phone app-power appointment system. The Biden administration has paired that process and other legal migration channels, including a program that allows migrants from four countries to fly to the U.S. if they have American sponsors, with the asylum restrictions to deter unlawful crossings through a carrots-and-sticks strategy. 

While it has arguably been responsible for ending, at least temporarily, large-scale illegal crossings and chaotic images at the U.S.-Mexico border, the Biden administration’s asylum crackdown has been derided as an election gimmick by Republican lawmakers and a draconian policy by migrant advocates, who are challenging the policy in court. 

In a conference hosted by the Migration Policy Institute last week, Homeland Security Secretary Alejandro Mayorkas challenged those critical of the asylum restrictions to find an “alternative proposal,” calling the situation at the border before the policy change “unworkable.”

“We have to understand the fact that the American public does want, does expect and does demand the delivery of order,” Mayorkas said, adding later, “And I would respectfully submit that, at least in particular times over the past three years, we haven’t had order.”