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. The company, too, recently partnered with the District of Columbia Board of Elections, one of about 3,000 public agencies that distribute voter and community information via Nextdoor.

“It gives us an opportunity to communicate with real people, not bots or trolls,” said Sam Liccardo, the mayor of San Jose, Calif., and an early advocate for the site. “That makes it a powerful tool.”