NASHVILLE (AP) — State Attorney General Bob Cooper has issued a legal opinion that a Republican-led effort to require photo identification to vote would violate the Tennessee and U.S. constitutions.

Cooper said in the opinion released Wednesday that without a provision to supply voters with free ID cards, the measure "unduly burdens the right to vote," and would constitute an unconstitutional poll tax.

But Cooper said other than the question of the costs involved, there's nothing about requiring a government-issued ID to vote that would run afoul of constitutional standards.

The Senate passed its version of the bill 21-11 in February, with only one Democrat voting for the measure. The chamber rejected Democrats' efforts to amend the bill to provide free IDs for poor voters and to exempt the elderly.

The companion bill sponsored by House Republican Caucus Chairwoman Debra Maggart of Hendersonville has been scheduled for a floor vote Thursday.

Democrats have voiced concern that the voter ID measure will intimidate or otherwise disenfranchise legitimate voters, while Republicans have argued that the measure would ensure ballot integrity.

"We do not want to keep anyone from voting," Maggart said. "Our goal is to make sure that our elections are honest and pure."

A separate Democratic measure to provide free IDs to people who can't afford them is advancing in the Senate, but its estimated price tag is nearly $200,000 in lost state revenues per year. Cooper's opinion notes that the Democratic measure "would appear to cure any challenge to the constitutionality" of the voter ID measure.

Maggart questioned Democrats' motivations for opposing requirements to show an ID before voting.

"It's disappointing that the Democrats go to great lengths to make sure that people can cheat when they vote," she said.