The union leading a strike against five Allina Health hospitals is changing how it will tally votes Monday night when more than 4,000 nurses decide whether to accept a three-year contract and return to work.

Results will be counted in aggregate for nurses at all five striking hospitals, rather than letting each hospital vote the contract up or down individually. Prior contract votes this summer were voted separately for United Hospital in St. Paul, Mercy Hospital in Coon Rapids, Unity Hospital in Fridley, and Abbott Northwestern Hospital and the Phillips Eye Institute in Minneapolis.

The change by the Minnesota Nurses Association (MNA) is based on a review of a 2001 contract document indicating that bargaining units for Abbott, Mercy, Phillips and United should negotiate together on contract items such as health benefits that are “conformed,” which means they must remain uniform across the hospitals.

Voting separately would be pointless because the document requires uniformity on those contract items across the hospitals, explained MNA spokesman Rick Fuentes.

Unity nurses weren’t represented by the union until after 2001, so the document doesn’t necessarily apply to them. However, the MNA board issued a directive this weekend to count their votes with the other hospitals.

“Monday’s vote is the collective opinion of the members,” Fuentes said. “Members are the union.”

The new legal interpretation prevents a potentially awkward result if nurses at one hospital vote to continue to strike while nurses at another vote to accept a contract. However, it also raises the question of whether the union was incorrectly tallying results by hospital for two contract votes earlier this summer, and for votes on other contracts over the past 15 years.

Fuentes said the earlier votes from the summer were recalculated: “The vote count for the earlier Allina proposals and authorizations to strike were so overwhelming that the outcome would’ve been the same.”

The outcome of Monday’s vote isn’t as certain, though, because the union’s negotiators haven’t advised nurses on whether to accept or reject Allina’s latest offer.

In two prior votes this summer, the union recommended that nurses reject the Allina contract offers, and they did so by more than the two-thirds majorities needed to authorize the seven-day strike in June and the current, open-ended strike that started Labor Day.

Contract approval Monday requires a simple majority of all votes cast.

Adding Unity to the combined tally is significant; the hospital has a younger nursing staff with less union history, and its nurses have been unnerved by recent changes at the hospital such as eliminating its obstetric services. Those factors could theoretically influence the contract vote results at Unity if they were counted independently.

The latest Allina contract offer provides the nurses with some guarantees about the cost of their health insurance through 2019 and addresses some of their concerns about workplace safety and staffing. On the other hand, the offer phases out their popular union-controlled health plans and doesn’t give the union the authority it sought over the Allina corporate plans to which the nurses will be switched.

Allina’s refusal to grant the union any say over the cost and quality of its corporate health plans prompted nurses to go on strike on Labor Day.

Nurses have now been on strike 36 days this year over the course of two strikes. The longest nursing strike in state history lasted 38 days in 1984.

Allina officials have called the latest contract a true compromise that includes 2 percent raises and a $500 bonus.

In a statement Sunday, Allina spokesman David Kanihan said the health system has no requirements on how the nurses’ votes are tallied and called it an “internal union matter.”