Sen. Bernie Sanders finally conferred his progressive imprimatur on presumptive Democratic presidential nominee Hillary Clinton Tuesday, but a new poll offers fresh evidence of continuing doubts among his legion of young supporters.

“Secretary Clinton has won the Democratic nominating process, and I congratulate her for that,” the Vermont senator said from New Hampshire, standing side-by-side with the former secretary of state. “She will be the Democratic nominee for president and I intend to do everything I can to make certain she will be the next president of the United States.”

“I wouldn’t say the Clinton-Sanders body language is the warmest I’ve ever seen. Nor is the endorsing language. But I’m sure Democrats will take it.”

Sanders, however, spent most of his speech talking about his political movement and the issues he cares most about, while deriding presumptive Republican nominee Donald Trump. He offered perfunctory praise for Clinton.

“I wouldn’t say the Clinton-Sanders body language is the warmest I’ve ever seen,” University of Virginia political scientist Larry Sabato wrote in a tweet. “Nor is the endorsing language. But I’m sure D[emocrats]s will take it.”

Sanders praised President Obama but said far too many Americans have been “left out, left behind, and ignored” during his administration. He said the 2016 campaign “is not really about Hillary Clinton, or Donald Trump, or Bernie Sanders, or any other candidate who sought the presidency. This campaign is about the needs of the American people and addressing the very serious crises that we face.”

Clinton made a direct appeal to the millennials who have so strongly back the senator.

“He has energized and inspired a generation of young people who care deeply about our country and are building a movement that is bigger than one candidate or one campaign,” she said.

Or so she hopes. On the day she accepted her former foe’s endorsement, however, a new poll shows she continues to struggle among Sanders’ core base of millennial voters — especially young whites and Hispanics. While 64 percent of blacks and 55 percent of Asian-Americans between the ages of 18 and 30 have a positive view of Clinton, just 26 percent of young whites and 49 percent of young Hispanics do.

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The survey was produced by GenForward, an effort of the Black Youth Project at the University of Chicago with the Associated Press-NORC Center for Public Affairs Research. Trump also gets low marks from millennials, but the youth vote means more to Clinton. President Obama won 60 percent or more of voters between the ages of 18 and 30 during his two runs for the White House. If Clinton cannot equal those margins — and maintain the turnout rate — it could jeopardize her election hopes.

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Sterling Beard, editor in chief of Campus Reform — a publication of the conservative-leaning Leadership Institute — said Clinton strikes many young voters as old and out of touch. Even though Sanders is older, Beard said, he offered a program that appeared fresh and exciting.

“She’s had a hard time breaking through, and I’m not sure that Sanders’ endorsement will make much of a difference,” he said.

Beard said students and recent college graduates have a hard time relating to Clinton.

“Here’s a woman who has made a substantial amount of money giving speeches, more than most of the students will hope to make for years … It feels like she’s saying, ‘Let them eat cake,'” he said.

On Tuesday, the Trump campaign sought to discredit Sanders.

“Bernie’s endorsement becomes Exhibit A in our rigged system — the Democrat Party is disenfranchising its voters to benefit the select and privileged few,” senior policy adviser Stephen Miller said in a statement.

Miller argued that Sanders was selling out those supporters who are concerned about special interests, unnecessary wars, and trade. He contended that Trump is the better standard-bearer on all of those issues.

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“The candidate who ran against [Trans-Pacific Partnership] is endorsing the candidate who helped draft the TPP,” he wrote. “The candidate who ran in opposition to globalization is running against the candidate who has led the push for globalization. The candidate who warned that open borders destroy the working class is endorsing the candidate with the most open borders policy in our history.”

The Trump campaign put out a series of statements highlighting Clinton’s past support for trade deals and her disagreements with Sanders over issues like the minimum wage and the Vermont senator’s “Medicare for all” plan. The campaign also highlighted Sanders’ past criticism of Clinton for her support in the 1990s for the Defense of Marriage Act.

Sanders, himself, alluded to his policy differences with Clinton even as he endorsed her.

“It is no secret that Hillary Clinton and I disagree on a number of issues,” he said. “That’s what this campaign has been about. That’s what democracy is about.”