When CNN’s Jake Tapper asked Bernie Sanders on Sunday if he wants to abolish the Immigration and Customs Enforcement agency, the senator was uncharacteristically vague. “I think that what we need is to create policies which deal with immigration in a rational way. And a rational way is not locking children up in detention centers or separating them from their mothers,” he said. “What we need is Trump to sit down with members of Congress and work on a rational program which deals with this serious issue.”

Sanders wasn’t the only potential 2020 presidential candidate on Sunday to refuse to endorse the abolition of ICE. “There’s no question that we’ve got to critically reexamine ICE and its role, and the way that it is being administered, and the work it is doing,” Senator Kamala Harris of California said on NBC’s Meet the Press. “And we need to probably think about starting from scratch.” But Sanders’s reticence was more surprising to his supporters and other liberals.

“Come on man!” wrote Splinter news editor Jack Mirkinson. “Let’s hope that the next person who gets the chance asks him why he is still taking such a weak and morally timid position on ICE.” Jeremy Scahill, co-founder of The Intercept, wrote that “Sanders is choosing to be on the wrong side of history on this issue.”

bernie sanders is wrong for not calling to abolish ice. — Hasan Piker (@hasanthehun) June 24, 2018

It is never good to idolize politicians. All of them need to be pressured. https://t.co/F7rA3SCvUt — Jonathan Cohn (@JonathanCohn) June 25, 2018

Created in 2003 by President George W. Bush, ICE has become increasingly unpopular among Democrats as evidence of its abuses continues to grow. Congressman Earl Blumenauer, who voted against the agency’s creation, wrote in a Medium post on Sunday that it’s time to “abolish ICE and start over.” On Monday, Congressman Mark Pocan of Wisconsin formally introduced legislation to disband the agency. Insurgent left-wing candidates like Alexandria Ocasio-Cortez, who is challenging Congressman Joe Crowley, have already begun to campaign on the issue.

Ocasio-Cortez belongs to a cohort of Democratic candidates who have positions in common with Sanders: Medicare for All, free higher education, and a $15 minimum wage. But by seeming to support ICE’s continued existence, Sanders has put a wedge between himself and those seeking to pick up the torch he carried in 2016. In the process, he’s undermining his position as the nation’s most prominent left-wing politician.