Chicago (CNN) Sen. Bernie Sanders brought it all back home this weekend, hosting a pair of boisterous rallies in two cities he credited for a political awakening that set him on a path that could, as he launches his second presidential campaign, deliver him to the White House.

In Chicago on Sunday night, Sanders again offered a rare public embrace of his roots, telling supporters at Navy Pier's Festival Hall that his years here as a student activist were "an extraordinary moment in my life and very much shaped my world view and what I wanted to do."

But even as Sanders broadened the scope of his stump speech to include more details about his youth, his message never strayed far from the core argument that would vault him to political stardom decades later. Sanders' vow to uproot and discard the private health insurance industry and deliver a single-payer system still drew the loudest applause from an already spirited crowd. The twin spectacles of Brooklyn and Chicago will also validate the belief among Sanders' allies that his support is stickier than many observers, including some wishful Democrats, might have hoped or predicted.

The Sanders campaign's goal now, it has become increasingly clear, is to lock in the base — which in the first week of his candidacy delivered more than a million volunteer sign-ups and a remarkable $10 million in small dollar donations — while seeking out fresh lines of connection to the unconvinced. In an interview before the trip, campaign co-chair Nina Turner described Sanders' task nearly a year out from the Iowa caucuses as "layering on top of what he did in 2016."

"The Democratic Party has adopted so much of his platform, so he won the moral argument in 2016," Turner said. "Now what he has to do is help people to see 'the why,' the reason why he's doing this, what drives him."

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