Bernie Sanders addressed a crowd of thousands at a beachside rally in Los Angeles last Saturday, capping a six-day swing through the most populous US state.

“Our campaign is not only about defeating [Donald] Trump, our campaign is about a political revolution,” Sanders said. “It is about transforming this country, it is about creating a government and an economy that works for all people and not just the 1%.”

The sight of the cheering crowd would have been hard to imagine just two months ago, as Sanders recovered from a heart attack and a fellow progressive senator, Elizabeth Warren, surged past him in the polls for the Democratic nomination.

But since then, Warren has slipped back, and Sanders has regained lost ground, demonstrating the resiliency of his leftwing campaign. Those strengths have some in the Democratic party wondering: could Sanders actually win the nomination the second time around?

According to the RealClearPolitics polling average, Warren was 12 points ahead of Sanders and virtually tied with the former vice-president Joe Biden in early October, shortly after Sanders’ heart attack. But since then, Warren has been slipping, and Sanders has pulled ahead of her. The polling average now shows Sanders in second place once again – averaging 19.3% in national polls, putting him eight points behind Biden and four points ahead of Warren.

“I believe people should take him very seriously. He has a very good shot of winning Iowa, a very good shot of winning New Hampshire, and other than Joe Biden, the best shot of winning Nevada,” Dan Pfeiffer, a former adviser to Barack Obama, told Politico. “He could build a real head of steam heading into South Carolina and Super Tuesday.”

Sanders does certainly seem to be learning from some of the pitfalls of his campaign in 2016, when he lost the Democratic nomination to Hillary Clinton. For example, Sanders was criticized for performing far better in the early-voting states of Iowa and New Hampshire, which are mostly white, before losing to Clinton in the more racially diverse states of Nevada and South Carolina.

This time around, Sanders has made significant efforts to reach out to voters of color, specifically Latinos. Polls show Sanders is the top choice among Latino voters, and the candidate held a Spanish-language town hall on Sunday in Las Vegas, Nevada, alongside Ocasio-Cortez. That outreach could prove critical in states like California, where Latinos make up about 40% of the population. Given that California awards nearly 500 delegates, about 10 times as many as the first caucus state of Iowa, performing well there is key to winning the nomination.

But Sanders’ greatest asset – a core of solid support – is also shared by Biden.

The Democratic presidential primary has proven surprisingly stable so far, with Biden continuing to lead even as candidates previously considered potential frontrunners, such as Kamala Harris and Beto O’Rourke, have exited the race.

Like Sanders, Biden has a solid base of supporters who have not abandoned him, despite negative coverage in recent months. The Vermont senator would need the dynamics of the primary to shift in some significant way to pull ahead of the former vice-president.

This is one reason why many centrist Democrats remain unconvinced Sanders can form a winning Democratic coalition.

“He can’t win the nomination,” Matt Bennett, the co-founder of the center-left thinktank Third Way, told Politico. Bennett and some of Sanders’ other critics have argued the senator’s ceiling of support is too low to ultimately defeat his primary opponents.

But if his 2016 campaign proved anything, it’s that Sanders thrives on low expectations. Many Washington insiders scoffed at Sanders’ first White House bid, until he fought Clinton to a draw in Iowa and scored a decisive victory in New Hampshire. Today, Sanders is offering the same message that he did four years ago: “Don’t underestimate me.”