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LAS VEGAS — Hillary Clinton’s campaign had one of its polling firms that specializes in the Latino vote assess the Nevada caucus results in an effort to rebut the claim by Senator Bernie Sanders that, though he lost over all, he won among Hispanics, a demographic that is crucial to the success of both candidates.

Mr. Sanders’s campaign said it viewed the loss in Nevada as a success because of the inroads he made with Latinos, and his claim to have broadened his coalition while edging into Mrs. Clinton’s support with Latinos, put the imperative on the Clinton campaign to try to show her strength among a demographic that will be critical in Super Tuesday states like Texas and Colorado.

The Clinton team report by Latino Decisions, obtained by The New York Times, says that the entrance polls from Saturday’s caucuses that showed Mr. Sanders defeating Mrs. Clinton by eight percentage points among Latinos, who made up 20 percent of Democratic caucus goers, “do not add up.”

The disagreement is a critical one for both sides: For Mr. Sanders proving his message resonated with Latinos debunks concerns that he only appeals to the white voters who delivered his strong showings in Iowa and New Hampshire and that he can be competitive in the larger, more diverse states that have contests in March. For Mrs. Clinton, holding on to her Latino support is an imperative as she seeks to solidify her delegate lead in places like Texas and prove she can draw a diverse coalition of voters who would be the linchpin of a general election.

“What we learned today is that Hillary Clinton’s firewall with Latino voters is a myth,” Arturo Carmona, deputy political director for the Sanders campaign, said shortly after Mr. Sanders’s loss Saturday to Mrs. Clinton by 5.5 percentage points.

“This is critically important as we move ahead to states like Colorado, Arizona, Texas and California,” he added.

Mrs. Clinton won Clark County, which includes Las Vegas and most of the state’s Latino population, by 11 percentage points. “It is not possible that Clinton lost the Latino vote yet won Clark County,” whose caucus goers were 30 percent Latino, by 11 points, the Clinton team’s memo said.

Latino Decisions says the data shows that Mrs. Clinton was victorious in the majority of the 40 precincts in Nevada that have more than 50 percent Latino registrants.

In precincts 4560 and 4559, both of which are in Clark County and are over 80 percent Hispanic, the polling firm says that Mrs. Clinton won seven and twelve delegates to Mr. Sanders’s one and four.

According to the memo, similar patterns occurred in East Las Vegas, where Mrs. Clinton had a heavy presence and enlisted surrogates like the Latina activist Dolores Huerta, the actress Eva Longoria and Chelsea Clinton, to rally volunteers, attend rallies or knock on doors.

Mrs. Clinton also swept the caucuses in the casinos, which drew predominantly Latino workers on a break from their jobs as blackjack dealers, cooks and housekeepers. The caucus at the Caesar’s Palace here was almost entirely conducted in Spanish with workers wearing “Estoy Contigo” (“I’m with you”) T-shirts.

The Latino Decisions pollsters, Matt A. Barreto and Gary M. Segura, known as experts at polling Hispanics, a difficult group to count because of their reliance on cellphones and at times transient nature, pointed to flaws in the Nevada entrance polls that the Sanders campaign relied on.

“How many of the Latino entrance poll questionnaires were completed in Spanish?” they asked. “The Latino electorate in Nevada is 35 percent foreign born.” They also questioned the entrance polls reporting that 40 percent of nonwhite caucus goers had college degrees, a figure that proved to be off by nearly double.

Ben Tulchin, a pollster for the Sanders campaign, called the Latino Decisions report “desperate spin” and said that younger Latinos who live all over the state overwhelming caucused for Mr. Sanders. The Sanders voters, Mr. Tulchin said, consisted largely of acculturated second and third generation English speaking Latinos who do not live in the predominantly Spanish speaking enclaves in Clark County that the Clinton campaign had intentionally focused on, he said, in order to make the results appear more favorable.

Losing the Latino vote would be a huge blow to Mrs. Clinton who unveiled her immigration reform plans here in May alongside the children of undocumented immigrants and has emphasized outreach to Latino voters. The Super Tuesday contest in Texas on March 1, where Mrs. Clinton hopes to solidify her delegate lead, will likely be made up of a 25 percent Latino and 20 percent African-American electorate.

In 2008, Mrs. Clinton won 63 percent of the Latino vote in the 16 Super Tuesday contests, compared to 35 percent for Barack Obama, according to exit polls.