Residents vote in Gorham in November 2018.

Maine will vote on Tuesday to officially select major-party presidential nominees and decide on a people’s veto effort that would repeal a law scrapping nonmedical exemptions for school vaccine requirements.

Here’s a guide to what’s on the ballot, how to vote and how the results will be counted.

What’s on the ballot?

The Democratic presidential primary and the effort to repeal the vaccine law are the two highest-profile statewide races on the ballot.

Five active Democrats are vying for the presidential nomination — Vermont Sen. Bernie Sanders, former Vice President Joe Biden, former New York City Mayor Mike Bloomberg, Massachusetts Sen. Elizabeth Warren and Hawaii Rep. Tulsi Gabbard. Candidates must receive 15 percent of votes to win a share of 24 pledged delegates to the national convention.

[How Maine Democrats will award delegates in Tuesday’s presidential primary]

President Donald Trump is unopposed on the Republican primary ballot. There are no certified write-in candidates in either party, so a vote for anyone who isn’t on the ballot will be counted as blank. Voters will have one choice in the Democratic primary because the effective date of a law expanding ranked-choice voting to presidential elections was delayed by Gov. Janet Mills.

Question 1 on Maine’s ballot would repeal a law passed last year by the Democratic-led Legislature that would repeal nonmedical exemptions to school vaccine requirements. It was passed as a response to rising vaccine opt-out rates among Maine schoolchildren, but opponents got enough signatures to put the question on the March ballot.

If the “yes” side prevails, parents would be allowed to exempt their children from mandatory vaccines for religious and philosophical reasons. A “no” vote upholds the law, meaning parents would no longer be able to opt their children out of mandatory school vaccinations unless they had a medical exemption.

[What you need to know before voting on Maine’s vaccine referendum]

There are a handful of races at the local level as well. Portland will vote on expanding the use of ranked-choice voting to city council and school board races. Part of Brewer will vote in a special election to replace the late Rep. Archie Verow, a Democrat. Former Rep. Garrel Craig, a Republican, is running against former Mayor Kevin O’Connell, a Democrat.

Who can vote in Maine and how do you register?

Mainers who will be 18 years of age or older before Nov. 3, 2020, can register to vote on or before Election Day in their cities or towns. Before Election Day, you can register at your municipal office. On Election Day, you can register at the polling place using same-day registration. Bring a piece of mail or a bill that proves your residence in the city or town if you’re a new voter. 

Who can vote in primaries?

Maine is one of 31 states that have either closed or semi-closed primaries, according to the National Conference of State Legislatures. It means that the state does not allow people registered in one party to vote in another party’s primary. 

In Maine, you must be a member of the party whose primary you’re voting in. However, unenrolled voters can register as a member of that party on or before Election Day. Members of other parties had until Feb. 14 to switch parties in order to vote in a primary of their choice. 

It means that while a Republican is not allowed to switch parties to vote in the Democratic primary — or vice versa — at the polls, an unenrolled voter can still join a party and vote in the primary of their choosing. They must remain a member of that new party for at least 90 days.

When and where do you vote on Election Day?

Polling places in cities and towns with more than 500 people must be open from 8 a.m. to 8 p.m., though many open by 6 a.m. to accommodate an early-rising work crowd. Polls must stay open from 10 a.m. to 8 p.m. in smaller towns, though virtually all of them open earlier.

If you don’t know where your polling place is, the Maine secretary of state’s office provides an online tool you can use to look it up by entering your address. You can also call your town office or visit their website with questions on Election Day logistics.

How do absentee ballots work?

The deadline to request an absentee ballot in Maine was Thursday, though there are exceptions for people facing an unexpected absence, those with disabilities or incapacities or who live on remote islands. All absentee ballots must be returned to a municipal clerk by 8 p.m. Tuesday.

Absentee ballots that have been submitted to a clerk cannot be recalled by a voter. People who voted for former Mayor Pete Buttigieg of South Bend, Indiana, who left the Democratic presidential primary on Sunday and polled second in Maine behind Sanders in a Colby College survey last month, have no choice but to leave their vote with him.

How will votes be handled for candidates who left the race?

Buttigieg and six others dropped out of the Democratic presidential race after qualifying for the Maine ballot — Minnesota Sen. Amy Klobuchar, billionaire activist Tom Steyer, New Jersey Sen. Cory Booker, entrepreneur Andrew Yang, author Marianne Williamson and former Massachusetts Gov. Deval Patrick.

In other Maine primaries, there is a process for candidates who drop out after qualifying for the ballot to tell the secretary of state to discount votes cast for them. That process does not apply to the presidential primary, so votes for these six presidential candidates will still be counted.

[How the end of Pete Buttigieg’s campaign is shaking up Maine’s primary]

This could have implications for the three remaining candidates — Biden, Bloomberg and Warren — who were sitting behind Sanders around the 15 percent threshold in the Colby poll. Klobuchar and Gabbard were in the single digits then.

How can I follow the results?

The Bangor Daily News is the only Maine news organization that collects results independently, while other news organizations use the Associated Press. You can watch results come in live on our dedicated page while using the panel on the right to navigate results by county and municipality. Results will start coming in after polls close.

The BDN and our partners at Decision Desk HQ will make calls in the presidential primaries and on the vaccine referendum. In the Democratic race, we will call a winner as soon as possible and then wait for enough results to come in before establishing a delegate projection. Question 1 will be called as soon as we are confident in a vote margin.

Michael Shepherd joined the Bangor Daily News in 2015 after time at the Kennebec Journal. He lives in Augusta, graduated from the University of Maine in 2012 and has a master's degree from the University...