Sen. Bernie Sanders is now the 12th person to launch a bid for the Democratic nomination for president of the United States. The oldest candidate to run for office in history and the most radical in a crowd of competitors, Bernie could seem like a long shot.

But to think that would mean you haven’t been paying attention because Sanders’ ground-game is exceptionally strong.

His residual 2016 infrastructure alone establishes him as a front-runner. He’s got an all volunteer meme-factory 400,000 strong, no less than three distinct organizations supporting his candidacy, and a grassroots donor base of over 200,000 so eager for another round of Sanders’ that they raised him $6 million dollars in the first 24 hours of his campaign.

While all of this is unprecedented, Sanders’ smartest move yet may be his intention to recruit “one million active volunteers” to join the campaign.

With over 600 days left until the election, there are enough candidates to field a football team and the competition is only likely to grow. The primary battle for the next Democratic candidate is very likely to last right up until the July convention, which means we have over 16 more months for the public to contest who deserves to be the nominee. And this is why Sanders’ volunteer strategy sets him apart.

Aside from the obvious capacity, a volunteer force of one million can provide for a campaign, ongoing visible action and volunteer support can build credibility for the Sanders campaign and platform in a way that money, ads and rallies cannot. There is nothing like a million people in action, reaching out to their friends, authentically advocating for Sanders and his policy in their own words to turn the tide of opinion in Sanders’ favor.

Momentum, a movement incubator and training organization, calls this sort of lasting engagement “active popular support.” It’s a decisive factor in popularizing new ideas and shifting public opinion. Active popular support can transform dominant thinking, making people more sympathetic to — and aware of — ideas they did not previously consider. It’s a key component of how social movements win their demands.

Its power is substantiated by data. Erica Chenoweth, professor of public policy at Harvard, found in her research that no social movement has failed to meet its demands if 3.5 percent of a population engage in sustained nonviolent action.

And what’s 3.5 percent of the roughly 28.8 million people who cast a ballot in the Democratic primary? One million. Look at that.

Now, Chenoweth’s research is not meant to be used for predictive purposes, but it does indicate that the sustained volunteer strategy — from a movement perspective — has the potential to be extremely successful for the Sanders campaign. It’s certainly a powerful start.

What’s more, the presence of volunteers draws more people to support the campaign and demonstrates that there is a place for them to fully engage. If the Sanders campaign can find a way to quickly plug in new volunteers they will be able to add even further to their organizational capacity and build even more support among the public for their candidate. All of this could very likely set Sanders out ahead of the rest in a very crowded primary field.

If this base of active support helps Sanders win the primaries — which it very well could — he would then be in an extremely good position to win the general election, countering the over $100 million Trump has already raised for his 2020 run. And Sanders will do this with priceless human infrastructure, setting up a true 1 percent vs. grassroots stand-off in the general election.

To be sure, Sanders still has obstacles ahead. He has yet to meaningfully or convincingly connect with voters of color, especially large portions of the older black population — the most staunchly Democratic population in the country. Sanders may have a hard time getting his volunteer army to be and look representative of the American public. Failing to attract a base consisting of the full diversity of America would be a disqualifying blow for him or any other serious Democratic contender for 2020 for that matter. But Sanders is identifying that active, recurring support is a foundational metric in his campaign. That means he’s not really building a campaign — he’s building a movement. And if Barack Obama or Alexandria Ocasio-Cortez have shown us anything, it’s that movements are what win elections.