Sen. Diana DiZoglio is defending her decision to vote in favor of advancing a bill that would make driver's licenses available to undocumented immigrants, leaning on the support of police chiefs in her district in the face of sharp criticism from Republicans who accused her of flip-flopping from her 2014 campaign position.

DiZoglio, a moderate Democrat from Methuen, said she was asked by the Major City Chiefs of Police Association to support moving the bill forward "to allow the conversation to continue through what will still be a very lengthy committee process."

She was one of 14 Democrats on the Joint Committee on Transportation to recommend a redrafted version of the driver's license bill last week on a strictly party-line vote. It's the furthest such a bill has ever advanced on Beacon Hill, and supporters of the legislation are optimistic about its chances this year.

"I voted yes in solidarity with our major city police chiefs association because the provisions in the bill would help law enforcement officers identify criminals who are here unlawfully and get them off the streets," DiZoglio said in a statement, shared with the News Service.

The blowback on DiZoglio highlights the politically sensitive nature of trying pass any legislation on Beacon Hill related to immigration, and the hurdles advocates may have to overcome if this is to be the year for a drivers license bill to get to Gov. Charlie Baker's desk.

The explanation from the first-term senator came after the Massachusetts Republican Party singled out DiZoglio for her vote, which was kept private by Senate leadership until the House co-chairman of the committee released the full vote to the News Service.

"Senate Democrats wanted to keep the public in the dark, and Sen. DiZoglio obviously would have preferred it that way," MassGOP Chairman Jim Lyons said in a statement. "What we have here are Democrats saying one thing and doing the other."

Lyons, who like DiZoglio lives in the Merrimack Valley, highlighted the position DiZoglio took against licenses for undocumented immigrants during her 2014 House re-election campaign.

"I do think that we need to make sure that everybody is documented and here legally before providing state resources," DiZoglio said at the time, according to a local newspaper The Valley Patriot.

Lyons said of Democrats: "They can't stand transparency and this is why."

DiZoglio pointed to a letter she received from the chiefs of police in Haverhill and Methuen supporting what they described as a "new" bill because of the changes made in committee.

The committee bill requires two forms of identification, including at least one with a photograph and one with a date-of-birth.

One form of identification that applicants would be required to provide would be either a valid foreign passport or a consular identification document. The second form of ID could be any of the following: a valid driver's license from another state or territory, a Massachusetts identification card, an original birth certificate or a valid employment authorization document issued by U.S. Citizenship and Immigration Services.

The list of documents in the bill resembles the lists in place in other states that allow undocumented immigrants to obtain driver's licenses, according to the bill's sponsor Rep. Christine Barber. It contrasts with language in previous versions of the bill that would have let the Registry of Motor Vehicles make documentation determinations.

"I did not and still do not support the previous version of the bill, as I felt the language was problematic and so did our chiefs association. I do, however, support advancing the redraft of the bill that was worked on with and endorsed by the Mass Police Chiefs Association," DiZoglio said.

When the police chiefs' association endorsed the bill, Chelsea Police Chief Brian Kyes, the president of the MMCC, said it would "promote trust between law enforcement and all the communities we serve and protect." "In order for our state’s police officers to best do their jobs and remain safe while doing so, they need to be able to identify who’s behind the wheel. All Massachusetts families need peace of mind knowing that the drivers on our highways and city streets have passed the same driving test and know the rules of our roads," Keyes said.

Haverhill Police Chief Allen DeNaro and Methuen Police Chief Joseph Solomon subsequently wrote in a letter to their legislators that the changes were the result of the committee's conversations with law enforcement.

"The preliminary support of this bill in no way is supportive of anyone entering our country or traveling through our communities illegally," they wrote. "The enforcement of proper immigration into the United States is regulated and policed by our federal law enforcement partners."

Both chiefs said they had received a briefing from RMV officials about how the registry would evaluate forms of identification prior to authorizing someone to take a licensure test, and how RMV employees are "trained on how to identify proper legal documents."

"Having the ability to properly license an individual will aid law enforcement officers in the Commonwealth in the identification of individuals they may encounter during motor vehicle interactions," DeNaro and Solomon wrote.

The chiefs said the bill was still "not in its best form," but insisted that it was important to keep working toward a bill that would "make the roadways of our Commonwealth safer."

"We believe additional safe guards are necessary to insure the accuracy of the information provided for those attempting to obtain a driver's license," they wrote.

Baker has cited his own concerns with the state's ability to "build the kind of safeguards into that kind of process" to ensure proper verification of an applicant's identity. He said last week that he continues to oppose the legislation, despite the changes made.