Nextdoor bills itself as a “private social network” that limits membership by address. It has increasingly become a place where people discuss politics and other civic issues.

When Hala Hijazi wanted her friends to meet London Breed, then a candidate for mayor of San Francisco, she invited the whole neighborhood.

Ms. Hijazi, a community organizer and consultant, lives in the city’s Marina District and is a member of Nextdoor, the neighborhood social media site.

She planned the meet-and-greet on the Marina’s bustling Chestnut Street and posted it on Nextdoor. One neighbor said he wouldn’t vote for Ms. Breed. She said another called the candidate “the worst.” Still others decided to vote for Ms. Breed after meeting her in person.

“Nextdoor is organic and, sometimes, it is going to be raw,” Ms. Hijazi said.

Ms. Breed won the mayoral election in June.

“People feel like only wealthy donors get access to politicians,” Ms. Hijazi said, adding, “I am doing this as a service to my community.”

Nextdoor, the neighborhood social media site, is partnering with local and state public agencies to bring voting information to more Americans. Here, the District of Columbia Board of Elections advises citizens on polling and where to vote.

Nextdoor has a reputation for being a home for cranky neighbors, people trying to find a reliable plumber, and frantic pet owners looking for their lost dogs.

But, as the saying goes, all politics is local. And with political engagement at an all-time high, Nextdoor is gearing up for the 2018 political primaries and beyond, partnering with public agencies and local governments, and encouraging civil political discourse in an increasing partisan America.

Fights between supporters of President Trump (and their nonsupporting neighbors) have driven some Nextdoor users away. To address those concerns, the San Francisco-based company is creating separate forums for neighbors who want to discuss national politics. Some cities, too, are frustrated with the service, saying there is no mechanism for local politicians to have a dialogue with constituents on the site.

Nextdoor bills itself as a “private social network” that limits membership by address, making it difficult for people not in a neighborhood network or, in some cases, an adjoining area, to participate. (A neighborhood can be as small as a few blocks.)

The company was founded in 2010 and said it is active in 175,000 neighborhoods, or about 85 percent nationwide. It is particularly prominent in San Francisco and, according to the company, especially popular with homeowners.

With so many users, Nextdoor sees a big market in voter registration and education. In March, it teamed up with Alex Padilla, California’s secretary of state, to provide voter information in five counties that adopted the California Voter’s Choice Act, which makes it easier for citizens to vote….