As the Massachusetts Legislature frantically tries to wrap up its business for the year, a showdown looms over illegal immigration. On the evening of July 27, Gov. Deval Patrick vetoed a proposal that would require anyone trying to register a car to provide proof of legal U.S. residency. The proposal is aimed at preventing undocumented immigrants from registering and operating vehicles. It comes in the wake of a high-profile accident in which a 23-year-old Milford man was killed by an illegal immigrant who was driving drunk.

In a letter to lawmakers, Patrick said that the measure was flawed and that it was inappropriate for state government to enforce federal immigration law.

But Rep. Rich Bastien (R-Gardner) said it’s a public safety issue, and in vetoing the bill, Patrick is trying to score political points with liberals.

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“I think that the governor is refusing to acknowledge that people who are here and are registering these vehicles but do not have a license are a threat to public safety,” Bastien said. “I’m deeply disappointed and I think that this will put the public safety at risk for the benefit for a group of people that Gov. Patrick is clearly trying to curry favor with. … It appears that he’s trying to bolster his credentials for a future run at office and that should never take place over public safety.”

The House and the Senate are expected to override the veto.

And the Legislature still has several high-profile items left to deal with before the end of July 31. Among them are a controversial “three strikes” crime bill and bills containing the state’s spiraling health care costs and funding transportation and infrastructure projects.