Why has DACA become such a sticking point in spending negotiations?

The debate over what to do with DACA recipients has opened up an immigration-related can of worms. For instance, Republicans have demanded that DACA reforms be paired with border security measures because they fear that legalizing an entire category of unauthorized immigrants could incentivize others to attempt illegal immigration.

Republicans and Democrats, however, disagree on what measures to take and how much funding to provide. Trump demanded $18 billion to fund his long-promised wall along the US-Mexico border, but Democrats have insisted that border security funding be confined to measures like fencing or surveillance technology.

Some Republicans, as well as Trump, have also demanded reforms to family-based immigration categories, which they refer to as "chain migration." Immigration hardliners such as Sens. Tom Cotton and David Perdue have previously proposed slashing legal immigration to the US by half, mostly by reducing the ability of US citizens and green card holders to sponsor their foreign relatives for visas.

The debate over "chain migration" reached the mainstream last December, after a suspected terrorist allegedly attempted a suicide bombing in a busy underground passageway in New York City. The suspect, 27-year-old Akayed Ullah, had immigrated to the US in 2011 through a family-sponsored visa category.

The Trump administration declared "chain migration" incompatible with national security and demanded Congress eliminate extended-family visa categories, which allowed "far too many dangerous, inadequately vetted people to access our country."

The diversity visa lottery met a similar fate. The program, which allots roughly 50,000 visas to people from countries that typically send few immigrants to the US, has long been a target for hardliners like Cotton and Perdue. But the program burst into the mainstream political debate after another recent New York City terror attack, in which the suspect received a visa to the US through the lottery years earlier.

Trump has since demanded that the lottery be eliminated, and has begun accusing foreign countries of using the diversity visa lottery to send their "worst people" to the US. The claim is false, as countries don't send immigrants through the program - people apply of their own volition.