From time to time, I will pluck from our NBC News video archives moments that have shaped our political culture today.

By now, we're used to Sen. Bernie Sanders, I-Vt., who has announced that he'll make a second run for the presidency, dominating the headlines. Most polls show him near the top in the Democratic race, and it seems at least possible he'll be able to enlarge his coalition enough to actually win the nomination this time.

It can be easy to forget just how far into the political mainstream Sanders has journeyed over the course of his career.

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Almost 40 years ago, he was a fringe character operating on the margins of Vermont's ever-quirky political world — the founder of a third party, the Liberty Union, who'd run and lost four statewide campaigns, never receiving more than 6 percent of the vote.

Then, in early 1981, he launched a campaign against the mayor of the state's largest city, Burlington. Running as an independent, Sanders benefited from pent-up frustrations with the incumbent, Gordon Paquette, and won the initial count by 22 votes. Paquette demanded a recount, which shaved a dozen votes off Sanders' margin but not enough to reverse the outcome. For the first time in decades — and just months after Ronald Reagan's sweeping national victory in the presidential election — a New England city would be governed by someone who called himself a socialist.

Sanders' victory brought him into the national spotlight for the first time. A UPI story explained that Sanders had "downplayed his radical philosophy" during the campaign and "traded his jeans for a coat and tie." Business leaders were said to be alarmed. "I think everyone's scared right now," the chairman of the state Democratic Party told The Associated Press at the time.

The election of a socialist mayor at the height of the Cold War caught the attention of NBC's "Today" show as well. On April 7, 1981, the day after his inauguration, Sanders was interviewed by Today contributor Phil Donahue, who introduced the new mayor by saying that everyone who'd read about his victory had the same question: "My goodness, how did this happen in good old, conservative Vermont?"

The passing of Pat Caddell, who wrote 'the memo'

When political strategist Patrick Caddell died recently, commentators noted the unlikely arc of his career: The same man who'd helped George McGovern take over the Democratic Party and Jimmy Carter win the White House had ended up, as the Washington Post put it, writing "the instruction manual" that put Donald Trump in the White House.

That manual was a 2016 memo prepared by Caddell that cited data showing deep and pervasive frustration among Americans toward their government and major institutions — conditions, he argued, that would make possible a populist insurgency that worked around the major party establishments.

"A new paradigm has emerged," he wrote. "It is a shift in political tectonic plates, the death rattle of the old order and the coming of the new political order."

Caddell was once the most celebrated Democratic political professional in America. In addition to McGovern and Carter, he was also closely aligned with Joe Biden in the 1970s and the 1980s. In more recent decades, though, Caddell migrated to the right (or, he would say, the Democratic Party migrated away from him).

What animated his view of politics was relatively consistent though. That 2016 memo mirrored many of the themes Caddell had stressed in another famous memo, one he wrote for Carter as his presidency spun out of control in 1979 — resulting in what came to be known as the "malaise" speech. The speech generated widespread derision and the controversy over it landed Caddell in the national spotlight. On the Sep. 6, 1979, edition of the "NBC Nightly News," anchor John Chancellor introduced this segment on "a very important young man named Pat Caddell, whose memo had changed the course of the Carter administration."