A Republican amendment that could leave hundreds of thousands of young immigrants open to deportations is running into stiff opposition in the House – a rare show of rank-and-file rebellion over the leadership’s catering to the right.

The measure – which would kill the Deferred Action for Childhood Arrivals program – is scheduled to come to the House floor Wednesday as part of a bill to fund the Department of Homeland Security through the end of September. But more than a dozen House Republicans have told the GOP whip operation that they will not vote for the amendment, according to people involved. These Republicans say the leadership is catering to the far-right elements of the party, and they disapprove of the underlying policy.

But there’s danger if the amendment, written by Rep. Marsha Blackburn (R-Tenn.), fails. Without that provision, there’s a chance that conservatives will not vote for the DHS funding bill, which would be an embarrassing loss for the leadership team. Republicans touted this process as the kind of inclusive approach they favor.

Rep. Jeff Denham (R-Calif.) said Tuesday that he opposes the Blackburn legislation, as well as a separate measure that, in part, rolls back immigration enforcement directives dating as far back as 2011. If those amendments are ultimately approved, Denham said he would oppose the underlying DHS funding bill.

“It’s disappointing to see an overreach,” Denham said of his own party.

The moderates in the GOP conference are taking issue, in particular, with a provision in Blackburn’s measure that would ban renewals under the current DACA program, which grants a two-year deportation reprieve and work permits for so-called Dreamers, young immigrants who were brought to the United States illegally as children.

Because their DACA status is temporary, blocking renewals – as the Blackburn language does – would effectively open up those immigrants to deportations.

“It’s mean-spirited,” one House Republican, granted anonymity to speak candidly about the situation. “Once people have come forward, and they have turned in all their information, their ID, where they live, they’re now planning their lives based on [the fact that] they can live here … it’s a step beyond what has to be done.”

The Obama administration has already issued a veto threat on the House Republicans’ immigration plan, and it’s nearly certain that it will not get the requisite 60 votes to advance in the GOP-controlled Senate.