A springtime lull in illegal border crossings could be the result of increased enforcement efforts by the Mexican government in a bid to help President Biden.

"The Biden administration responds to bad optics," Lora Ries, director of the Heritage Foundation's Border Security and Immigration Center, told Fox News Digital. "The numbers reached a new high in December, and it’s no coincidence that’s when the secretaries met with Mexican officials and then, all of the sudden, the numbers dropped."

The comments come as the number of illegal crossings at the U.S. southern border with Mexico have continued to decline from an all-time high in December, dipping from nearly 302,000 that month to just over 193,000 in March. That number has declined further in April, according to a report in the Washington Post, with border agents encountering roughly 130,000 migrants attempting to illegally enter from Mexico.

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President Biden with US flag behind him, left; migrants wade over river near border wall, right

President Biden has recently touted the decline in illegal border crossings. (Getty Images)

While the Biden administration has touted the decline, a USA Today report this week noted that the unusual lull in crossings could have more to do with increased Mexican efforts. Most notably, the report notes, is the country’s recent efforts to round up migrants heading for the border and instead bus them south.

The Mexican government's effort has hurt migrants' chance of making it to the U.S. border successfully, according to the report, which notes that Mexican police have been intercepting migrants on highways, train routes and at airports and bussing them to the southernmost part of Mexico. Once there, migrants are faced with the choice of attempting to make the long journey north again or abandoning the effort altogether, a tactic that has at the very least caused a delay for some migrants.

Mexico has made a noticeable push in recent months to beef up its immigration enforcement and crack down on attempts to cross its border with the U.S., including a move in February to station troops near the infamous San Judas Break, a hole in the border barrier that thousands of illegal migrants had been using to sneak their way from Mexico into the United States. Another February military operation saw Mexican troops shut down a popular smuggling point on the San Diego-Tijuana border.

The sudden crackdown came shortly after a call by Biden to Mexican President Andres Manuel López Obrador in late December, when Biden asked for help at the border, according to a report from the New York Times, resulting in a delegation led by Secretary of State Antony Blinken traveling to Mexico to meet with the Mexican president.

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A Mexican decision to start enforcing its own immigration laws more strictly soon followed, the report notes, which has made it more difficult for migrants to use the country to reach the United States.

The Biden administration once again touted its continued cooperation with Mexico on the border, releasing a joint statement along with López Obrador detailing a Sunday phone call between the two leaders.

"The two leaders discussed how to effectively manage hemispheric migration, strengthen operational efficiency on our shared border, and thereby improve the security and prosperity of citizens of both countries," read the statement. "In the short term, the two leaders ordered their national security teams to work together to immediately implement concrete measures to significantly reduce irregular border crossings while protecting human rights. President Biden and President López Obrador also pledged to advance initiatives to address the root causes of migration throughout the Western Hemisphere."

Migrants press up against border gate as Guardsman looks on

A group of over 100 migrants attempting to enter the U.S. illegally rush a border wall on Thursday, March 21, 2024. (James Breeden for New York Post / Mega)

When reached for comment by Fox News Digital, a White House spokesperson credited both its continued work with regional partners and "enhanced enforcement efforts by the U.S. government."

"Even without significant action from Congress, DHS is maximizing its enforcement operations," the spokesperson said. "Since May 12, DHS has removed or returned more than 690,000 individuals – the vast majority of whom crossed the southwest border. 690,000 removals and returns is more than every full fiscal year since 2011."

According to Ries, that sudden cooperation on the border could be the result of a political deal.

"I’m sure the Biden administration and Biden perhaps himself has said to him, ‘look, do you want me to win reelection? You don’t want Trump back in office,’" Ries said.

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Ries noted that such a move was not a "free favor," noting that the Mexican president demanded $20 billion in aid from the U.S.

That aid was demanded by the Mexican president at a news conference shortly after the first meeting between himself and Biden administration officials, with López Obrador issuing a series of demands, including that the U.S. give $20 billion to Latin American and Caribbean countries. The Mexican president also called for the U.S. to grant work visas to 10 million Hispanics who have worked in the U.S. for over 10 years, end sanctions against Venezuela and end its embargo with Cuba.

Mexico's president Lopez Obrador speaking at podium

Mexican President Andrés Manuel López Obrador speaks at a military parade in Mexico City on Aug. 13, 2021. (AP Photo/Fernando Llano, File)

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Curt Mills, the executive director of the American Conservative, also believes the sudden lull in activity at the border can be traced to Mexican enforcement, telling Fox News Digital that there has been "more effective pressure" on Mexico in recent months.

"This is an administration that essentially ignored the issue, for the first part of [Biden’s] tenure, didn’t think it was an issue, didn’t give it high priority," Mills said, adding it was only after widespread outrage had spread about the administration’s failures at the border that it began to act.

Ries argued that the administration relying on Mexico to beef up enforcement allows it to avoid angering progressive allies who oppose stricter border measures, while at the same time limiting the political fallout of a continued crisis.

"He is certainly trying to play both sides in an election year. He has to appease his radical left base that wants an open border, but he also knows that border security is the number one issue for Americans," Ries said. "He needs to make the border numbers look a little better."

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Meanwhile, the White House pointed to a failed bipartisan immigration bill as part of the reason for stymied efforts.

"The Administration spent months negotiating in good faith to deliver the toughest and fairest bipartisan border security bill in decades because we need Congress to make significant policy reforms and to provide additional funding to secure our border and fix our broken immigration system," the spokesperson said. "Congressional Republicans chose to put partisan politics ahead of our national security and rejected what border agents have said they need."

Get the latest updates on the ongoing border crisis from the Fox News Digital immigration hub.