The emergence of Sen. Bernie Sanders (I-Vt.) as a viable presidential nominee for the Democratic Party has sparked some deja vu for those who came of political awareness during the George W. Bush era.

Vermonters of a seemingly liberal bend, with grassroots armies of supporters and a robust Internet fundraising apparatus, seem to have a way of capturing the Democratic Party's heart. Sanders and former Gov. Howard Dean are dissimilar in many respects, and that's before even mentioning that Dean supports Sanders' opponent, Hillary Clinton, in this campaign. But their trajectories have parallels, from the unexpected rise to the (in Sanders' case, burgeoning) push back from party elites.

Sanders hasn't caused nearly the same amount of panic that Dean did among establishment Democrats in 2003-2004. That could simply be because the expectation is that Sanders' campaign will ultimately collapse like Dean's did in the weeks before the Iowa caucus.

But if you talk to folks working on behalf of the senator, they don't see themselves at risk of Dean-like pitfalls. They're not even studying his playbook for clues.

“We haven't really used his campaign as a model or looked to it for lessons,” Sanders’ top strategist, Tad Devine, told the Huffington Post not too long ago. “I'm not sure if Bernie talked to him about this but I doubt it. It’s just so different now than it was in 2004.”

From a structural level, Devine is right. Sanders’ fundraising apparatus is more robust than Dean’s, in part because the nature of the Internet now allows easier access and certainty when it comes to recruiting online donors. The issues dominating the process are also fundamentally different from 2004 and, arguably, more suited to Sanders’ strengths -- more focus on economic policy than the prosecution of the Iraq War.

But Dean, in his recent interview with "Candidate Confessional," hinted at something that could still trip Sanders up the way it did him. At some point, Dean explained, he had to show voters that he could, in fact, be a president and not just an insurrectionist. But he couldn’t do it; he was too habituated to his role as an outsider.

“I was giving them something they deeply valued, which was hope. And to pull back and become the establishment figure that I knew I had to become to become president was really hard to do,” Dean said. “I knew I had to make the turn. And I couldn’t do it. I just couldn’t do it.”

Dean ended up finishing third in Iowa and lost the New Hampshire primary to John Kerry shortly thereafter. His stumbles were largely his own making. But it’s certainly true that the party establishment helped facilitate the fall, with outside groups running ads and spreading rumors against him, and lawmakers warning of a perilous down-ballot calamity were he to end up atop the ticket.

Echoes of that have begun popping up in 2016 with Sanders. The senator received a round of fairly critical commentary from traditionally liberal writers after the debate on Sunday, focused both on his policy proposals and the messaging he’s deployed on the trail.

Whether voters take those cues and sour on him as they did Dean is the fundamental question in the weeks ahead. Devine, who worked for Kerry in 2004, seemed confident that there wouldn’t be a similar trip up in the closing weeks.

“Howard was popular with hardcore [Democrats], and Bernie is very strong with more independent [Democrats], the way Kerry was,” he said. “Bernie's challenge is not to make the turn in his message, but to make sure more people hear his message … and to ensure that voters view him as credible as a potential nominee and president. Dean had to deal with the reality that 9/11 was still the driving force in American politics in '04, and he did not offer enough reassurance on that front and it cost him.”

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