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LAS VEGAS — The first deep dive into Latino political donations found that Bernie Sanders got the most financial support last year. It also found a drop in donations as some candidates, such as Julián Castro, left the race.

Latinos contributed almost $23.7 million to Democratic presidential candidates last year, much of it in small-dollar donations averaging $15.75, according to an in-depth analysis of campaign finance data by Plus Three, a technology company that researched Latinos' contributions to Democratic presidential candidates.

It shared its latest findings with NBC News ahead of their release.

According to the data, Sanders, an independent senator from Vermont, dominates in the race for Latinos' dollars, snagging $8.3 million in 2019, or 36 percent of all contributions. Sanders leads in just about every state, except Sen. Amy Klobuchar's home state, Minnesota, where she beats him by about $3,000. He also leads in most major cities.

The analysis also finds that, as candidates leave the race, Latino contributions aren't yet shifting to other candidates. Candidates don't appear to be trying to scoop up donors who endorsed their rivals, and Latino contributions are slowing.

"We've definitely seen a drop-off in Latino giving in the last quarter," said Juan Proaño, co-founder and CEO of Plus Three, the first company to conduct an in-depth study of Latino political contributions for a presidential race.

The analysis is interactive and available to the public. It breaks down the data in many ways, including giving by ZIP code and Spanish surname. For example, in Texas, Latinos with the last names García and Rodriguez were the biggest givers.

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There's a lot of distance between Sanders and the next closest candidate, former Rep. Beto O'Rourke of Texas, who dropped out of the race in November. Even so, O'Rourke managed to out-raise other candidates for the year, at $2.7 million.

O'Rourke is followed by Sen. Elizabeth Warren of Massachusetts, who got $2.1 million; Pete Buttigieg, the former mayor of South Bend, Indiana, at $2.02 million; Castro — the only Latino who ran, who exited last month — at $1.8 million; former Vice President Joe Biden, at $1.4 million; Andrew Yang, who dropped out Tuesday, at $1.3 million; and Sen. Kamala Harris of California, who has also left the race, at $1.3 million.

Klobuchar trails at $319,000, about 3.6 percent of Sanders' haul. Sen. Cory Booker of New Jersey, who also dropped out last month, raised about $287,000.

Sanders has been trying to build on the strong young Latino following he attracted in 2016. Having won the popular votes in the Iowa caucuses and the New Hampshire primary, he heads into Latino-heavy Nevada, which holds its caucuses on Feb. 22, in position to rake in more money, although Warren and Buttigieg have been working Latinos in the state and Biden remains a favorite with older Latinos.

Buttigieg, Klobuchar and businessman Tom Steyer planned to participate in a town hall held by the League of United Latin American Citizens (LULAC) and Telemundo in Las Vegas on Thursday night. Sanders was to participate via video conference.

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Sanders built a large ground game in Iowa aimed at Latino voters. According to an analysis of 32 high-density Latino caucus locations, about 52 percent of votes were for Sanders, compared to 15 percent for Biden, 14 percent for Buttigieg and 11 percent for Warren.

The research found that Sanders managed to out-raise his opponents even though he averaged smaller donations from Latinos, at $13.37. That compares to Klobuchar, who had the highest average, at $27.69.

From the first half of the year to the second, contributions dropped by about $3.3 million, almost 25 percent, and the average gift also dropped.

Some of the decline has come as the number of candidates has dwindled, so fewer are raising money. The departures of Castro, who's from San Antonio, and O'Rourke, who's from El Paso, Texas, have also meant the exit of Latino supporters.

"The Latino donors, as the candidates have dropped out, they've either dropped off or they are waiting to see who emerges," Proaño said. "The other candidates haven't done a good job at all to solicit those donors."

It's also possible that the holiday season diverted spending, he said.

Latinos in Castro's hometown led giving

Latinos in San Antonio gave $820,000, the most among major cities, besting Los Angeles by about $1,000. Miami, which some consider the northernmost Latin American city, ranked ninth, at $359,177.

The ranking at the top for San Antonio is significant because Latino earnings and wealth in Los Angeles and Miami are greater than in the south Texas city. Latinos from El Paso made their city third, giving $606,494. New York was in fourth place, with $515,263.

The drop in dollars for some candidates can be seen in a comparison of money raised in the second quarter — April through June — and the final quarter, October through December.

Sanders raised $2.4 million in the second quarter, with a high of $1.27 million in June. Warren raised $850,897. Her highest month was June, at $421,041.

In the fourth quarter, Sanders raised $1.97 million. Warren had $466,778, a drop of nearly half.

"She's underperforming herself by a lot," Proaño said.

Castro endorsed Warren in early January soon after he dropped out, and he has been an active surrogate for her. He brought staff, some donors and connections in the Latino community with him. This week, Warren's campaign launched a five-city Texas tour that started in San Antonio, focused on rallying Latinos.

Data from January aren't yet available to assess how Castro's move to Warren has affected her contributions from Latinos.

Meanwhile, Latino contributions to Buttigieg and Biden had slowed significantly at the end of last year.

In the second quarter, Buttigieg raised $1.09 million, compared to $336,563 in October through December.

As of the end of last year, Buttigieg "was bottoming out in the Latino community," said Proaño, which he also saw with Harris and Booker before they ran into financial hardship and dropped out.

Biden's best month was April, when he raised $434,024, for a second-quarter total of $816,277. His three-month total in October through December was $368,801, less than he raised in April alone.

"His third quarter [July through September] was abysmal, less than $100,000 in every month," Proaño said.

Klobuchar's best month was February, at $48,883.05. Yang's best month was December, when he raised $311,949.91.

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