NASHVILLE (AP) — An ongoing fight over using public dollars to pay for private school tuition turned tense Tuesday, as a key Tennessee House vote didn't get officially tallied for 40 minutes until a single lawmaker changed his no to a yes, while Senate leaders advocated for a drastically different version.

The action marked the latest wrangling over Gov. Bill Lee's education savings account proposal — a voucher-style program that would let families use up to $7,300 in public funds to pay for private school tuition and other expenses.

In the House, Speaker Glen Casada refused to accept a 49-49 vote tally that would have spiked the voucher bill. Instead, the vote was not declared official for nearly 40 minutes until Casada had successfully lobbied a fellow Republican, Rep. Jason Zachary, of Knoxville, to change his vote on the electronic tally board, passing the measure 50-48.

The last-minute switch was secured behind closed doors on a House patio, where reporters could not go, with Casada, Zachary and other aides and lawmakers.

Zachary later said he eventually agreed to the change because Casada promised him the final version of the voucher bill would exempt his elected home seat of Knox County from being able to distribute education savings accounts. Zachary and some other lawmakers want their home counties removed from the program. Some fear that participating local public schools would receive fewer public dollars in the voucher program.

However, the House version advanced Tuesday includes Knox County and three others in the voucher program. Currently, no legislation exists that would fulfill Casada's promise to Zachary. Instead, GOP leaders say they'll need to tinker with the voucher bill moving through the Senate.

In that version, Senate leaders have already drastically amended the voucher bill not only to strip the program down to apply only to metro Nashville and Shelby County — which also includes Memphis — but also remove a legally suspect provision about verifying immigration status of parents. The Senate also would allow certain homeschooling families to participate.

With the two drastically different proposals, the House and Senate will likely need to convene a special joint panel to negotiate a compromise before adjourning for the year.

House Republicans defended their secretive actions Tuesday, while Democrats argued Casada's move likely violated the state's constitution.

Democratic Caucus Chairman Mike Stewart described Casada's actions as an "unconstitutional act of trickery" and hinted of a possible lawsuit challenging the legality of the vote.

"That's not a conversation we can have out here in front of everybody," Zachary said, adding that speaking in private with the speaker prevented "distractions" from getting what he wanted.

Supporters countered that while the move was rare, it was not unprecedented. They pointed to previous speakers who refused to acknowledge a vote for hours while attempting to drum up support.

"We just let them think a little bit about what they were doing and how they would be hurting the future generation of the children in the state," Casada said.

Tennessee lawmakers have long attempted to expand vouchers, but until this year have faced repeated opposition from lawmakers concerned about taking limited resources from the state's public schools.

Matters shifted after key changes in House leadership, a slew of new lawmakers and the election of Lee, a first-time politician who campaigned for governor on school choice. The education savings account bill has since become Tennessee's top legislative battleground, with Lee supporters calling the proposal the administration's most important bill of the session.

Now, a stripped-down bill may allow only the state's two most populous counties — both Democratic strongholds — to offer education savings accounts, even though nearly every lawmaker in those counties voted against the bill. All 10 of Nashville's representatives, all Democrats, voted "no." In Shelby County, nine Democrats and two Republicans voted against the bill, while two Republicans and one Democrat voted in favor.

Five states allow some sort of education savings account: Arizona, Florida, Mississippi, Tennessee and North Carolina. The Nevada Supreme Court struck down its state's law after ruling that the funding mechanism was unconstitutional.

In Tennessee, the existing program is fairly small. Parents of students with certain disabilities can withdraw their children from public school and then receive up to $6,000 to pay for private educational services.