I’ve been advocating a lower voting age for some time, but it always seemed a theoretical exercise. Residents of San Francisco on Tuesday have a chance to make it a reality if they support Proposition F, which would lower the voting age for local elections to 16.

It has a good chance of passing: The only recent poll shows that a slim plurality favor the measure.

San Francisco would be the third US city to lower the voting age to 16, after two Maryland suburbs, Takoma Park and Hyattsville, took the plunge in 2013 and 2015, respectively. As the first large city to take this step, San Francisco would encourage others to consider following.

It’s even possible to imagine a full state going along, meaning that 16-year-olds could vote in national elections, too, since states are in charge of the electoral system. The 26th Amendment to the Constitution only says that the minimum voting age cannot be set higher than 18; governments are free to go lower than that.

They should. We believe in universal voting rights for two reasons: All citizens should be able to support their own interests, and all citizens should be able to enjoy self-government. Both apply as much for 16-year-olds, or even 14-year-olds, as they do for those who are 18 or 21 or, for that matter, 50.

The practical reason for giving more teenagers the franchise is that voting and not voting are habit-forming. As it stands, 18 is an unfortunate age for first eligibility. People tend to vote more if they have stable lives rooted in their communities, and this isn’t a great description for many people who are 18 to 21.

In addition, teenagers already participate in politics. When I was in Des Moines for the Iowa caucuses earlier this year, I met several high school students who had traveled there to work at the phone banks and walk the precincts for the candidates they supported. I’ve seen too-young-to-vote volunteers in many other campaigns, from mayoral races on up.

No one would ever try to ban that participation, which can have far more impact on an election’s outcome than an individual’s vote. Yet those same young citizens are denied the franchise.

Yes, I know what you’re thinking: Most teenagers would vote however their parents told them to. And yes, many teenagers would be uninformed and malleable. But just as many adults are uninformed and vote reflexively for the party their parents supported. Maybe young teenagers wouldn’t make the most sophisticated choices. But we value democracy not because it produces the “best” policy. Sometimes it doesn’t. The value is in giving all interests a say in government decisions and providing an opportunity for political participation.

If it were up to me, I’d lower the voting age to at least 14, so that everyone would have an opportunity to cast at least one ballot for president before graduating from high school. Presidential elections are the best mobilizers to make voting a habit.

San Francisco isn’t going that far. But 16 is better than 18. The question then will be: Who is next?

By Jonathan Bernstein

Jonathan Bernstein is a Bloomberg View columnist. He taught political science at the University of Texas at San Antonio and DePauw University. -- Ed.

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