Hillary Clinton needs to forge a connection with Democratic voters during the party’s first presidential debate on Tuesday night, according to David Axelrod.

“Her task, as the undisputed front-runner and putative nominee, will be to give the Democrats reason to believe,” Axelrod wrote in an op-ed for CNN.

“There has been a strange disconnect between Clinton and Democratic voters this year and a sense of resignation, rather than excitement, about her candidacy,” said Axelrod, a former chief strategist for President Obama.

“This challenge is reflected in the contrast between the large, enthusiastic crowds Sen. Bernie Sanders [I-Vt.] is drawing with his populist crusade and the more tepid reaction Clinton is generating,” he added.

Axelrod said Sanders is giving Clinton a fight because he comes across as genuine on the campaign trail.

“Whatever else you think about him, Sanders is utterly authentic,” he said. "And right now, that is Clinton’s challenge.”

“It has been exacerbated by her clumsy, ever-evolving approach to the email issue — something certain to come up again in the debate — and her rapid-fire race to the co-opt Sanders’ positions on trade, climate change and other issues that fire up the Democratic base.”

“Clinton’s mission on Tuesday is to rise above the tactical and present a coherent, value-laden vision that will make her flood of policy papers seem like something more than positions of convenience,” he added.

The op-ed from Axelrod, who has become a persistent Clinton critic, comes as the 2016 Democratic presidential field prepares for its first televised debate on Tuesday night in Las Vegas.

Axelrod, who worked in the Obama White House, said Clinton needs a strong performance in the debate, given the possibility of Vice President Biden launching a third Oval Office bid.

“As Clinton is well-aware, if she were to stumble, the day after would bring a new round of hand-wringing and Biden-longing among anxious Democrats,” he said. 

“But, for now, this debate and nominating race remain Clinton’s to lose.”

Axelrod has repeatedly criticized Clinton for lacking a clear message for voters on the 2016 campaign trail.

“[She must be] running for a purpose and not just a promotion,” he said last December before Clinton launched her campaign. "You have to stand for something, you have to fight for something, and people need to know what that is.”

Clinton has struggled to move past the controversy over her private email server usage during her tenure as secretary of State.

Critics say the device prevented accountability of her actions and may also have jeopardized sensitive national intelligence.