PORTLAND — TrueBallot, the company the city hired to help with the ballot counting in November’s ranked-choice mayoral election, will hold a demonstration this evening.

The company will demonstrate how voters can cast their ballots and provide information on how the ballots will be counted. The event will begin at 6:30 p.m. in the State of Maine Room in City Hall.

In ranked-choice voting, voters can cast a ballot for their top choice for mayor, but also rank as many of the other candidates as they wish. Ballots will be counted and if no candidate has a majority, the low vote-getter will be dropped from the count and his or her voters’ second-choice votes allocated to the other candidates. The process continues until one candidate emerges with a majority.

There are 15 candidates for mayor. The city released a sample ballot this week with the candidates listed alphabetically. After each candidate’s name is a row of 15 ovals for voters to fill in to indicate their ranking.

The city will count ballots in the first round of tabulations on election night, Nov. 8. If no one has a majority, TrueBallot officials will go to City Hall on Nov. 9 and use a device to take an image of each ballot. Computer software will then “read” the images and allocate the votes.