The Arizona senate postponed voting on a critical immigration ballot measure that would authorize the arrest and deportation of illegal immigrants who unlawfully cross the Arizona-Mexico border outside of the state’s designated ports of entry.

The vote, originally slated to be held on Tuesday, was pushed back to next Wednesday because Republican state senators did not have enough votes to pass their measure. At the time, a Republican lawmaker was absent from the Arizona senate, weakening the already-slim 16–14 GOP majority’s chances of approving the measure.

The Republican-backed proposal, similar to Texas’s S.B. 4, would empower state law enforcement to arrest illegal immigrants and local judges to deport them, effectively making illegal immigration a state crime. H.C.R. 2060, or the Secure the Border Act, would also make it a crime to present false documents when applying for public benefits or a job and strengthen penalties for criminals who sell fentanyl that causes the death of another person, according to its legislative text.

If approved by the state senate and house, the ballot question will be up for a vote in November.

Meanwhile, the bill has obstacles ahead. Republicans are facing dissent from one of their own members, Senator Ken Bennett, who has proposed multiple changes to the ballot measure that may fail to win over his conservative colleagues.

Bennett proposes that the legislation should not punish so-called Dreamers who crossed the border under DACA, or the Deferred Action for Childhood Arrivals program, years ago. Created in 2012, DACA protects illegal immigrants who entered the U.S. as children from deportation and gives them work permits. Bennett also has concerns about how children and families will be impacted.

The measure classified most of the offenses as felonies; Bennett said he seeks to reduce those punishments to a Class 1 misdemeanor on the first offense.

Moreover, the state senator wants the border-enforcement measure to strictly focus on the border rather than authorize detentions for illegal immigrants statewide.

“To give state, county and local law enforcement the tools to arrest and detain people who are entering illegally – the farther away you get from the border, the harder it is to maintain the probable cause that I think you’d need to make those detentions,” Bennett said.

If certain parts of the bill’s language are not changed, Bennett may not support his party’s measure. “There are some things if we don’t get, I won’t vote for it,” he told reporters, without revealing what those requirements were.

Living United for Change in Arizona, a pro-immigrant advocacy group, and Democratic state lawmakers strongly oppose the measure, likening it to S.B. 1070. Much of the 2010 law, commonly known as the “Show Me Your Papers Law,” was struck down by the U.S. Supreme Court in 2012 because it conflicted with federal immigration law. The Court upheld one provision, enabling Arizona police to inquire about an immigrant’s legal status during lawful encounters.

Critics such as the American Civil Liberties Union say the provision, like the border-security ballot measure, leads to racial profiling and discrimination.