BOSTON (SHNS) – Republican candidate for governor Geoff Diehl and his running mate Leah Allen on Monday cautioned of what they see as unintended consequences if state lawmakers approve a bill making immigrants without legal status eligible for driver’s licenses.

Ahead of a Thursday Senate vote, the pair of former state representatives told reporters they worried about incentivizing illegal immigration and about the Registry of Motor Vehicles’ ability to verify that applicants are who they say they are.

“There’s a way to come to the country legally and it is through the naturalization process, and becoming a citizen should be the way that you are rewarded with all the services that you can get, including a driver’s license,” Diehl said outside the State House.

The Senate bill (S 2851), similar to legislation that cleared the House in February, would allow immigrants without legal status to apply for and obtain a standard driver’s license if they show a foreign passport or consular ID and certain other documents.

Bill supporters say Massachusetts would be joining 16 other states with similar policies. They say the measure would make the roads safer by making sure more drivers are properly trained and insured, while also helping people who are currently ineligible for licenses get to jobs and family obligations, especially in areas without significant public transit infrastructure.

Sen. Brendan Crighton, the bill’s Senate sponsor and Transportation Committee co-chair, said last week that the bill directs the secretary of state’s office to develop regulations ensuring that license applicants who are in the country illegally are not registered to vote under the state’s automatic voter-registration law.

Allen said she wanted to see data from the RMV showing how officials plan to prevent people who are in the country illegally from registering to vote, and Diehl questioned whether there would be insurance impacts for other ratepayers if people in the country illegally are unable to get their cars insured.

The candidates were joined by Maureen Maloney, whose son Matthew Denice was 23 years old when he was killed by a drunk driver in the country illegally.

Maloney, who has testified before lawmakers on immigration enforcement matters in the past and was featured in a web ad in Diehl’s 2018 challenge to U.S. Sen. Elizabeth Warren, said she was “pleading with the Senate” not to pass the bill and called it a “slap in the face to the legal immigrants who have done it the correct way, who have waited their turn.”

The House passed its version of the bill with sufficient support to override a possible gubernatorial veto, and the measure’s Senate proponents have said they hope to do the same.

Diehl described Gov. Baker, who has voiced concerns with the policy, as the “first line of defense” against it becoming law. Diehl said that if the bill does make it onto the state’s books, “this would be something that Leah and I would try to address as well once we’re in office.”

A recent poll found Bay Staters were split on the issue. In the Suffolk University/Boston Globe poll of Massachusetts residents, conducted from April 24 to April 28, about 47 percent of respondents said they opposed legislation that would allow people without legal immigration status to be eligible for driver’s licenses, with 46 percent in favor and about 7 percent undecided.

That same survey found the Democratic candidates for governor, Attorney General Maura Healey and Sen. Sonia Chang-Díaz, each with strong leads over Diehl and his primary opponent, Chris Doughty.

Healey led Diehl 54 percent to 27 percent in the poll, with 17 percent undecided. In the match-up with Chang-Díaz, 29 percent picked Diehl while 45 percent went for the state senator, and 24 percent were undecided.

In a hypothetical three-way contest pitting Diehl and Healey against Gov. Charlie Baker running as an independent, Baker came out on top with 37 percent to Healey’s 28 percent and Diehl’s 17 percent.

Doughty has also pushed back on the idea of license access for immigrants without legal status. In February, as the House prepared to take up its bill, he launched an online petition in opposition.

Republican auditor candidate Anthony Amore has also come out in opposition to the license bill, penning an op-ed in Monday’s Boston Herald that cites his experience as an immigration officer in the 1990s and raises fraud concerns.

“I agree with Gov. Baker, who has expressed serious concerns about loopholes that enable voter registration by noncitizens,” Amore wrote. “We prefer the current state law which requires ‘proof of lawful presence.'”