Democratic Gov. Janet Mills will allow a bill to become law next year that extends Maine’s landmark ranked-choice voting system to be used in presidential elections.

Her decision to wait until next year means that the system won’t be used in next year’s March 3 presidential primary contests, but it could be used in the general election.

In a statement, the governor said she did not sign the bill on Friday because the Maine Senate did not appropriate any funds to implement the system or clarify “how the will of the voters would be reflected in the selection of delegates and in the ultimate nomination of a candidate for President.”

The governor’s citing of delegation allocation is a reference to how primaries ultimately determine a party’s presidential nominee. Unlike winner-take-all general elections, primaries are used by parties to choose delegates who then vote for presidential candidates at the national convention.

Mills had until midnight Friday to either sign, veto or announce that she was holding the bill until next year. The proposal passed the Democratic-controlled Senate during a special one-day session held last week — a move that took many by surprise because the session had been called by the governor to pass a slate of bond bills. The proposal had initially stalled in June because of concerns about its costs to implement and its effect on municipalities.

In a statement, the governor said holding the bill will give the Legislature “an opportunity to appropriate funds and to take any other appropriate action in the Second Regular Session to fully implement ranked-choice voting in all aspects of presidential elections as the Legislature sees fit.”

Mills had agonized over whether to sign the bill, citing its costs and potential complications with how it will affect selecting delegates for political parties at their national conventions.

This year, the Democratic National Committee has set a minimum threshold for determining which candidates can earn delegates at 15 percent. Those rules could have complicated ranked-choice voting, where the goal is to produce a winner who obtains a majority of the votes.

The system, which is used when there are three or more candidates, allows voters to rank candidates in order of preference. If a candidate obtains an outright majority after the first count, they win. If not, election officials eliminate the last-place finisher from contention and redistribute that candidate’s votes based on voter’s second-choice ranking. The process continues until someone obtains a majority.

That process had raised questions about how Maine election officials would handle a Democratic primary with multiple candidates.

Mills had also worried about how the process would affect the general election, particularly because of Maine’s unique way of distributing electoral votes in the Electoral College. Unlike all other states, Maine and Nebraska award its four electoral votes based on tabulations in each of the state’s two congressional districts. In other words, a candidate can win a single electoral vote even if he or she loses statewide if they prevail in one of the state’s two congressional districts.

Such splits are rare, but one occurred in 2016 when President Donald Trump won the 2nd Congressional District. As a result, Trump received a single electoral vote, while Democratic candidate Hillary Clinton won the other three for winning statewide and the 1st Congressional District.

Mills, in her statement, appeared convinced that the system would work in the general election.

“The law will still require that one presidential elector be chosen from each congressional district and two electors to be chosen at large, but ranked-choice voting could well make a difference if there are more than two candidates and if no candidate achieves more than fifty percent in the first round of tabulation in one of the two Congressional districts or in the at large count,” she said. “The two at-large electors would both represent the one winner in the statewide tabulation for President.”

Maine became the first state to use ranked-choice voting in statewide elections in 2018 after voters ratified the system via a ballot initiative in 2016. The state is now the first to use the system in presidential elections.

David Farmer, a spokesperson for the Committee for Ranked Choice Voting, said in a statement that the group was disppointed that the governor didn't sign the bill into law.

“With an unprecedented number of candidates seeking the Democratic nomination, voters could be forced to pick just one and that’s too bad," he said. "However, RCV will be used in next November’s presidential election and in future primaries and general elections for President moving forward.”

Originally published Sept. 6, 2019 at 4:27 p.m. ET.