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KENT, Ohio — Sen. Bernie Sanders returned to the campaign trail Saturday to pitch Hillary Clinton to his base of young supporters — but not all millennials are with her yet.

“I’m still undecided,” said 23-year old Kent State University student Feagin Oliver when asked who she would support in the presidential election.

Oliver came to see Sanders’ second Ohio surrogate event of the day at Kent State University because she supported him passionately in the primary. But the Vermont senator has not yet been able to convince her to support Clinton.

“It’s gonna take a little while to earn trust back for sure,” said Oliver, who explained that leaked emails from the Democratic National Committee showing preference for Clinton during the primary still factors into her decision.

Related: Sanders: Trump Must Not Become President

Oliver is an example of the very type of voter Sanders is tasked with delivering for Hillary Clinton in November.

While recent polls show Clinton capturing more millennial voters compared to her Republican rival Donald Trump, voters aged 18-34 are hesitant to fully back Clinton.This key demographic was crucial to President Barack Obama’s two electoral victories.

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Instead, some are exploring third-party options such as Green Party candidate Dr. Jill Stein or Libertarian candidate Gary Johnson. “[Dr. Stein] is definitely on my radar and might be on my ballot in November,” Oliver told NBC News.

Hillary Clinton and Sen. Bernie Sanders stand together during a campaign rally in Portsmouth, New Hampshire, on July 12, 2016. BRIAN SNYDER / Reuters

Sanders, who consistently beat Clinton in the primaries among young voters, has been working to draw them back to the Democratic nominee with an anti-Trump/fear-Trump message combined with a push to get out the vote.

“What Trump is doing is trying to undo all of the gains that people fought and died for for hundred of years in creating a nondiscriminatory type of society,” said Sanders at the University of Akron, blasting the GOP nominee for his history of questioning Obama's birthplace.

“We can argue about the issues, but we cannot in the year 2016 accept bigotry as the cornerstone of any candidate running for president of the United States,” he added sharply.

Sanders implored students not to stay home on Election Day.

“I hope that you will not only come out and vote … I hope you’ll get involved in the process, register your friends!” said the Vermont senator in Akron.

“Too many young people are not registered to vote,” he added.

But the two primary messages coming from Sanders on the trail — keep Trump from the White House, get out the vote — may not be enough to get his supporters to turn out for Clinton.

Sanders cautioned against protest votes during an appearance on MSNBC's "Morning Joe."

As Sanders praised Clinton in Ohio, he highlighted their agreed-upon policies regarding free public university and college tuition for low income families and their shared dedication to picking a SCOTUS nominee who would be against the Citizens United decision.

The bulk of Sanders’ surrogate speeches more often focus on his own policy priorities and positions with Clinton's name tagged on the end assuring his crowds that she "understands" the importance of progressive issues.

Though making the case for Clinton was perhaps the most appealing message to those on the fence.

"Obviously, I'll never vote for Trump,” Jake Knapp, 22, a former Kent State student said after hearing Sanders speak.

“I’m not quite there yet [with Clinton]," Knapp noted, pointing to Clinton’s refusal to reveal transcripts of paid speeches the former secretary of state delivered on Wall Street.

Nonetheless, Knapp admitted hearing Sanders praise Clinton in person did help "move the needle" for him today.