When early voting began last week, the Sanders campaign sent a neon truck blasting local Spanish radio out onto the Las Vegas streets, urging people to show up at dozens of early caucus sites. They attracted hundreds of people to a soccer tournament, then offered rides to caucus sites to anyone who showed up.

After months of knocking on doors in largely Latino neighborhoods in Las Vegas, on Saturday morning, the Sanders campaign said it sent text messages and phone calls to every Latino registered as a Democrat or independent in the state.

For months, the Sanders campaign has boasted that it was the first to organize and advertise in largely Latino neighborhoods, not just in Las Vegas, but in Des Moines and east Los Angeles. Many people who showed up at the caucuses wearing Sanders buttons and stickers said his campaign was the only one they ever heard from. Latino political activists — including those backing other candidates — routinely applaud the Sanders campaign for doing the kind of expensive, labor intensive outreach they have been trying to convince other candidates to do for years.

Former Mayor Michael R. Bloomberg, who has virtually unlimited resources, is also investing in Latino outreach and competing aggressively in Super Tuesday states, which could cut into support for Mr. Sanders. He has already spent more than $10 million on Spanish-language advertising.

Mr. Sanders’s appeal seems particularly strong in the West, where his ability to harness not just Latinos, but also liberal black and Asian-American voters could portend a strong showing in California, which will award more delegates than the four early voting states combined.

The Sanders team has long said that California, where early voting is already underway, is a cornerstone of its campaign. It has invested roughly $6.5 million in advertising there so far, including more than $1 million for Spanish language advertising. A poll from the Public Policy Institute of California released last week showed Mr. Sanders with 30 percent of the vote, and Mr. Biden in second, trailing by nearly 20 percentage points.