DES MOINES — In Council Bluffs, he broke from his prepared remarks to warn his supporters that they were up against not only Republicans and Wall Street and corporate interests — but “the establishment Democrats,” too. In Des Moines, he thanked the crowd for nearly delivering an upset victory against Hillary Clinton in the Iowa caucuses four years ago. And in Iowa City, he made a point to note that before those votes had even been cast, “my opponent then had 500 superdelegates.”

The crowd of 1,800 answered on cue with a round of boos.

When Bernie Sanders traveled to Iowa late this week for a trip to three of the state’s major media markets — his first as a presidential candidate in 2020 — there were moments that could have been mistaken as flashes of the last primary contest. Staffers and volunteers wore lanyards with an old slogan, “Not me. Us,” which presented an implicit contrast in 2016 with the popular Clinton catchphrase, “I’m with her.” And on stage, Sanders repeatedly referenced a “50 percent” in the Iowa caucuses, recalling the perennial frustration among Clinton supporters whenever Sanders would refer to the results as a “virtual tie.” (Sanders won 49.6% of the vote. Clinton won 49.9% and took home two more delegates.)

For some Democratic voters who didn’t support Sanders in 2016, a primary contest that lasted until the eve of the convention and left Democratic voters bitter and divided, the 77-year-old Vermont senator is still fighting the last war.

For Sanders, 2016 is a crucial backdrop for the story he’s trying to tell in the early stages of his second presidential bid: Four years ago, he told supporters in Council Bluffs, Iowa City, and Des Moines, he launched a campaign that started with no donors or endorsements or national infrastructure and rose from the bottom of the polls — all on the basis of ideas that, as he tells it, “establishment politicians and mainstream media considered to be radical and extreme.”

At every stop here, Sanders marked Iowa as the spot “where the political revolution began.”

“When I first came here to campaign four years ago, not a whole lot of people in Iowa knew who the junior senator from Vermont was,” he said. A year later, his near-win in the caucuses led to victories in 22 states and a campaign that secured more primary votes from young people, as Sanders has become fond of noting, than Clinton and Donald Trump combined. “And by the way, those ideas we talked about here in Iowa four years ago that seemed so radical at the time — well, today, virtually all of those ideas are supported by a majority of the American people.”

Many of those ideas — namely, his rhetoric on Wall Street and corporate interests and his proposals for a Medicare-for-all health care system and a $15 minimum wage — have also been embraced by much of the Democratic presidential field. Leading candidates like Sens. Kamala Harris, Elizabeth Warren, and Cory Booker talk more like Sanders about Democratic policy and ideology than like the woman Democrats elected as their presidential nominee four years ago.

On stage in Iowa, Sanders was still railing against the very “establishment Democrats” he’s helped influence and worked alongside in the years since 2016. In Council Bluffs and Iowa City, at his first two stops of the trip, he cast the party elite as one in a long list of powerful forces that would, he warned, oppose his campaign, including the Republican Party, Wall Street, the pharmaceutical companies, the fossil fuel industry, and the “prison industrial complex.”

Jeff Weaver, a senior Sanders strategist who served as campaign manager in 2016, said that while the Democratic Party has seen “a great transformation” in Sanders’s own image, “a small sliver of the party that adheres to failed neo-liberal policies will fight very hard to stop Bernie Sanders and this grassroots movement.”

Asked to identify those forces, Weaver named staunch Clinton supporter David Brock, former Clinton aide Zac Petkanas, and the “literati on Twitter.”

Brock, a veteran operative who runs a network of well-funded Democratic research groups, has suggested that major donors wouldn’t support Sanders in a general election. And in a recent Politico story about the senator’s use of a private plane, Petkanas described the senator as “his royal majesty, King Bernie Sanders," arguing that Sanders only left his “plush D.C. office” and “brand new second home on the lake” to campaign for Democrats in 2016 "if he was flown around on a cushy private jet like a billionaire master of the universe." (Sanders, whose aides did propose the use of a private plane paid for by the Democratic National Committee ahead of the general election, held 39 rallies in 13 states on behalf of Clinton’s campaign.)

“It’s the tip of the spear,” Weaver said of Brock and Petkanas’ comments.

In 2020, the presence, even in theory, of forces that dismiss or oppose Sanders already seems to figure as necessary fuel for the kind of defiant, anti-establishment energy that propelled his first presidential campaign.

“They say Bernie Sanders’ time has passed,” said Abshir Omar, a Democratic socialist and former city council candidate who introduced the senator in Des Moines.

“But look around you today: Look at this energy, look at this enthusiasm. We are not done.”

Taking the stage at his last stop of the trip, Sanders took a more conciliatory approach, promising to run a positive campaign against his Democratic rivals and, in the face of a loss, support the eventual Democratic nominee.

“I hope very much two things: One, that the nature of our campaign is not belittling people — it’s not opposition research, it’s not attacking people — but it’s an important discussion,” he told a crowd of 1,300 at the state fairgrounds on Saturday. “The second point that I want to make is that I’m going to work as hard as I can — and I think we stand a really good chance of winning this nomination — but if we do not win, I will strongly support the Democratic nominee.”

“We must defeat Donald Trump,” Sanders said.