Kamala Harris's presidential campaign is quietly building out its national footprint.

The California Democrat has taken a more methodical approach than some rivals in amassing ground troops. On Tuesday, Harris' team will take another step, launching a national training program designed to harness volunteer energy on the ground that it could later tap into, according to a preview of the plan shared with POLITICO.

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Democratic presidential candidates are using various techniques to enlist grass-roots support — from paying staffers to collect sign-ups to marshaling online networks to organize coffees and watch parties. The door-to-door outreach is a crucial, yet often overlooked, element of their efforts to gain an advantage in the early voting states.

Harris, who piloted her online program in Iowa under the banner of "Camp Kamala," will put volunteers through one or two sessions a week as part of its national effort to train future precinct captains and volunteer leaders.

"By building a grassroots program that not only engages supporters but also provides the skills and training to organize their own communities wherever they are," said Anatole Jenkins, Harris' deputy national field director, "we are planting seeds for our future organizing efforts to win this primary and elect the first woman president."