The Supreme Court is taking up the Trump administration’s plan to end legal protections that shield 660,000 immigrants from deportation, a case with strong political overtones amid the 2020 presidential election campaign.

All eyes will be on Chief Justice John Roberts when the court hears arguments Tuesday. Roberts is the conservative justice closest to the court’s center who also is keenly aware of public perceptions of an ideologically divided court.

It’s the third time in three years that the administration is asking the justices to rescue a controversial policy that has been blocked by several lower courts.

The court sided with President Donald Trump in allowing him to enforce the travel ban on visitors from some majority Muslim countries, but it blocked the administration from adding a citizenship question to the 2020 census.

Roberts was the only member of the court in the majority both times, siding with four conservatives on the travel ban and four liberals in the census case. His vote could be decisive a third time, as well. With Congress at an impasse over a comprehensive immigration bill, President Barack Obama decided to formally protect people from deportation while also allowing them to work legally in the U.S.

But Trump made tough talk on immigration a central part of his campaign and less than eight months after taking office, he announced in September 2017 that he would end DACA.