After prompting the longest government shutdown in history, President Donald Trump’s divisive proposal for a border wall has taken a back seat in recent days for negotiators in Congress who are seeking to avoid another crippling closure. The latest talks have focused on another immigration issue that has quietly exploded in recent months: Record numbers of migrants being held in cramped detention centers.

Under orders to end the process that the president calls “catch and release,” the authorities have arrested and jailed tens of thousands of migrants since Trump took office, and Republicans would like it to stay that way.

Democrats argue that ordinary immigrants around the country are being unnecessarily plucked from their families and jailed, and newly arrived migrants are being forced to wait unreasonable lengths of time in harsh detention centers.

At issue is how much money the budget should provide for detention. Without more money, the authorities will have to scale back on arrests.

“We’ll be releasing gang members. We’ll be releasing individuals convicted of domestic violence and drug crimes,” said Matthew Albence, deputy director of Immigration and Customs Enforcement. “We will not be able to respond to as many calls as we do today. And in fact, in many of these calls, we’re going to tell them, ‘Just release them,’ because we have no choice.”

Democrats point out that more than a quarter of current ICE detainees are not subject to mandatory detention under the law.

Both Republicans and Democrats are citing competing data to claim that the new budget proposal advances their goals. Here’s what the plan really says:

Why has the border wall taken a back seat?

Months of brinkmanship between Congress and the White House over the border wall have distracted from the issue of detention, which has now reached a breaking point, with the authorities being urged by the White House to arrest more immigrants than they can currently afford to detain.

With little support for a robust border wall on either side of the aisle within Congress, Republicans and Democrats have moved on to detention, which is also expensive, and has implications for recent border crossers as well as immigrants with firmly established roots in the United States.

Why are so many people being detained?

Trump’s strict enforcement agenda has pushed the population of detained immigrants to the highest levels in history, with the authorities sweeping into immigrant-heavy locales to arrest vast numbers of people who entered the country illegally, as well as those who have violated the terms of their visas (usually through criminal convictions), making them deportable.

Under sweeping policy changes introduced by Trump, ICE has gone after immigrants who were once not targeted, repopularizing workplace raids, arresting community leaders, and using previously frowned upon tactics to ferret out anyone who can be expelled from the country. As a result, the average daily population in immigration detention for the 2019 fiscal year has reached 45,890. ICE currently has funding to house only 40,520 people.

How are Republicans and Democrats both claiming a win?

Republicans are saying that they secured money for 5,000 additional immigration detention beds, while Democrats are saying that they managed to bring down detention numbers by 17.4 percent. Technically, both are true. Here’s why:

Both parties agreed in the proposal to fund an average daily population for 2019 of 45,724 ICE detainees, or about 5,000 more than the 2018 budget provided — allowing Republicans to claim their success.

But in order to reach that average by Sept. 30, the last day of the fiscal year, ICE will gradually have to decrease its detained population to 40,520, which represents about a 17 percent decrease from the 49,057 who are currently detained.

Why are some Republicans saying that the proposal allows for 58,500 beds?

Republican aides suggested in internal communications that the number of detained immigrants could reach 58,500 under the proposal through a process called reprogramming, which allows agencies to adjust their budgets to address unforeseen emergencies.

Under reprogramming, federal agencies can take money that has been appropriated by Congress for specific matters, and use it to fund other things. And though it is meant to be used sparingly, the Department of Homeland Security has often used reprogramming to fund extra detention beds.

Though it is a common tactic, Democrats argue that the amount of money that would need to be reprogrammed in order to reach 58,500 detention beds, $750 million, would be unprecedented.

And they argue that the congressional committees that are now controlled by Democrats would never approve such a large amount.

The Department of Homeland Security has historically deferred to such committees for approval before reprogramming funds, though it is not technically required.

What else is in the budget proposal?

The deal provides funds for $1.375 billion in physical barriers along the border, far less than the $5.7 billion that Trump requested for his border wall. The money could be put toward 55 miles of new fencing, using only “currently deployed designs.”

The proposal also provides funding to revamp holding facilities that are used by Customs and Border Protection, which came under renewed scrutiny after the deaths of two young migrant children around Christmas.

And it would refund Obama-era programs that were eliminated under Trump, which had provided alternatives to detention for certain immigrants. Those who had been enrolled in the programs were allowed to roam freely, using GPS ankle bracelets and other incentives devised to make sure they showed up for court.

This article originally appeared in The New York Times.