Sen. Kamala Harris just put Democrats on the spot with a challenging question: What should be done about ICE?

The California Democrat, a possible 2020 presidential candidate, said she is so frustrated with how federal Immigration and Customs Enforcement treats migrants that the government should consider “starting from scratch” with an undefined overhaul of the 15-year-old agency.

However, she and a growing number of Democratic lawmakers talking about making changes to immigration-law enforcement, including House Minority Leader Nancy Pelosi of San Francisco, are avoiding calling for the step that the party’s more progressive members have turned into a Twitter hashtag: “#Abolish ICE.”

“I think there’s no question that we’ve got to critically re-examine ICE and its role and the way that it is being administered and the work it is doing,” Harris told MSNBC over the weekend. “And we need to probably think about starting from scratch.”

It’s about as far as any prominent Democrat has gone in reaction to a year-and-a-half’s worth of Trump administration efforts to limit legal and illegal immigration, culminating with the uproar over its “zero tolerance” policy that for two months resulted in children being separated from their parents at the border.

As Democrats reacted with anger, President Trump accused the party of favoring “open borders.” That’s where some Democrats privately fear they could be vulnerable, if they adopt the “abolish ICE” stance that progressives are quickly establishing as a litmus test for the left.

House Republicans could easily pass a Bill on Strong Border Security but remember, it still has to pass in the Senate, and for that we need 10 Democrat votes, and all they do is RESIST. They want Open Borders and don’t care about Crime! Need more Republicans to WIN in November! — Donald J. Trump (@realDonaldTrump) June 25, 2018

Sean McElwee, a political data expert who created the #AbolishICE hashtag in February 2017, has little patience for rhetorical moderation when it comes to immigration-law enforcement and says momentum is on the left’s side. He said his Data for Progress firm counted 3,600 tweets using the #AbolishICE hashtag in the first five months of the year — and 25,000 so far in June.

Nineteen current Democratic challengers in House races — and four Democratic incumbents — have called for shuttering ICE. Matt Haggman, who is facing former Clinton Cabinet member Donna Shalala in a Florida Democratic congressional primary, just released a campaign ad that called for “closing ICE down,” saying, “Donna Shalala, she’s had her chance. It’s time for a new day.” It’s a sign of how the issue is being used as a dividing line between progressives and more moderate Democrats.

It's official -- we're going up on TV!



Donna Shalala has had her chance, it's time for new voices, new leadership, and new energy in Washington. As your Congressman, I'll fight to shut ICE down. It's time for a new day. pic.twitter.com/1kHLJ211iB — Matt Haggman (@matthaggman) June 19, 2018

McElwee said it’s also a sign that people are craving more definitive political positions. Noting that Republicans control Congress, the White House and most state legislatures, he said, “It sure hasn’t hurt them to call for the abolition of the IRS or Obamacare.”

Harris may not have called for abolishing ICE, but even a proposal to rethink the agency’s mission is likely to put the issue on the Democratic agenda in this fall’s election and the 2020 presidential race. Harris has been positioning herself for a possible run, traveling to early primary states and raising money for other Democrats, and told MSNBC that she was “not ruling out” a presidential bid.

“What President Trump has done on immigration is the most extreme of his positions, so it makes sense to stake out a strong oppositional standpoint on that,” said Eric Schickler, a professor of political science at UC Berkeley. “By doing this, she is signaling that she’s going to be aggressive on this issue. It puts pressure on other Democratic candidates to come up with a clear stance.”

Harris’ challenge to revamp ICE, Schickler said, is likely to create a dividing line between liberal and moderate Democrats on immigration-law enforcement, much as the issue of a single-payer model on health care has cleaved the party. “Either they sign onto it or not,” Schickler said.

Harris is not “embracing abolishing” ICE, nor is she calling for ending enforcement of the nation’s borders, spokesman Tyrone Gayle said Monday.

However, she does not yet have a fully realized vision of what a revamped ICE would look like. Instead, she and other Democrats want to re-examine the nation’s immigration policy. That discussion would include reviewing the agency’s mission, how ICE has performed those duties and what it should focus on.

Harris was one of the leading Senate critics of ICE even before the “zero tolerance” tactics began dominating the news this month. In May, she and Rep. Pramila Jayapal, D-Wash., introduced legislation calling for a moratorium on new ICE detention facilities. In March, Harris called for a decrease in funding for ICE, and in December, she grilled Department of Homeland Security Secretary Kirstjen Nielsen about whether the agency would target young undocumented immigrants temporarily protected from deportation by the Deferred Action for Childhood Arrivals program.

Calling for an ICE reboot, however, is a leap ahead. When Harris was asked during an interview on MSNBC in March whether she thought ICE should even exist, she said, “ICE has a purpose, ICE has a role, ICE should exist. But let’s not abuse the power.”

McElwee said Harris has “moved pretty dramatically left since that. I would bet you good money that Bernie Sanders supports abolishing ICE in two months or less.”

On Monday, some House Democrats started down that path.

Rep. Mark Pocan, D-Wis., said he will introduce legislation, possibly as soon as Wednesday, that would abolish the agency over the next six months. It would establish an independent commission that would suggest how to restructure ICE and how to transfer some of its functions to other departments.

Pocan’s legislation, however, will go nowhere as long as Republicans control the House. “There are hurdles,” conceded spokesman Ron Boehmer.

Other Democrats were staking out positions that more closely resembled Harris’ idea of “starting from scratch.”

Pelosi “believes that ICE has been on the wrong end of far too many inhumane and unconstitutional practices to be allowed to continue without an immediate and fundamental overhaul,” said her spokesman Drew Hammill. “No one can watch ICE play such a central role in the heartbreak and horror of family separation without reasonably concluding that a drastic overhaul is desperately needed, and soon.”

Sen. Dianne Feinstein, D-Calif., stopped only a little short of endorsing a “drastic overhaul.”

“We’ve seen cases of ICE resorting to extreme measures like following families to school, shutting down agricultural operations during harvest season and deporting immigrants who are longtime residents of their communities and pose no threat to public safety,” Feinstein said in a statement to The Chronicle. “It’s clear that we need to rethink how our immigration laws are enforced in the face of repeated overreach. Immigration laws can be enforced without these tactics.”

Some conservatives like Mark Krikorian, executive director of the Center for Immigration Studies, which favors restrictions on migration to the U.S., actually welcomed Democrats calling for an end to ICE. But not for the same reason as progressives.

Democrats calling to abolish @ICEgov 'is a gift to Republicans' https://t.co/RPZGcOLf7P — Mark Krikorian (@MarkSKrikorian) June 25, 2018

Such calls, Krikorian tweeted Monday, would be a “gift to Republicans.”

Joe Garofoli is The San Francisco Chronicle’s senior political writer. Email: jgarofoli@sfchronicle.com Twitter: @joegarofoli