FILE - In this April 4, 2018, file photo, Sen. Bernie Sanders, I-Vt., speaks at a rally commemorating the 50th anniversary of the assassination of the Martin Luther King Jr. in Memphis, Tenn. Look closely enough at the 2018 midterm campaign and you'll see the seedlings of a Democratic presidential campaign to reclaim the White House. (AP Photo/Mark Humphrey, File)

Bernie Sanders’ political career is a living reproof to the idea, attributed to the ancient Greek philosopher Heraclitus, that the only constant in life is change.

After eight years as mayor of Burlington, 16 years as Vermont’s sole representative in the U.S. House of Representatives and nearly 12 years as a U.S. senator, Sanders’ outrage is undiminished when it comes to the struggles of working class families and the growing divisions in society between the few who possess extreme wealth and the many who do not. Indeed, his announcement last week that he intends to seek a third six-year term in the Senate was thematically of a piece with all that has come before: “Our struggle to create a government which represents all of us and not just the 1 percent — a government based on the principles of economic, social, racial and environmental justice — must continue,” the 76-year-old senator said.

And, as he did in 2006 and 2012, Sanders intends to seek the Democratic nomination in the primary, respectfully decline it if he wins, and run as an independent in the general election, meanwhile accepting the hearty endorsement of the Vermont Democratic Party. Thus are accommodations made to finesse the senator’s continued insistence on being identified as an independent, though he caucuses with the Democrats in the Senate.

What has changed remarkably, though, is the degree to which people outside Vermont take notice of what an independent “democratic socialist” (that’s small ‘d’, small ‘s’) from a tiny, deep-blue state thinks. When, for example, Sanders released a video last week calling out Amazon and its fabulously rich CEO Jeff Bezos over low wages and exhausting working conditions for employees of its fulfillment centers, the company responded the same day with a defense of its policies and an invitation to Sanders to visit. Sanders in turn accepted the invitation with thanks and added for good measure, “I remain deeply concerned about Amazon, an enormously profitable corporation, paying workers wages that are so low that they are forced to depend on federal programs like Medicaid, food stamps and public housing for survival.”

This new-found influence stems, of course, from Sanders’ out-of-left-field bid to capture the 2016 Democratic presidential nomination. Although he did not ultimately succeed, he secured a remarkable 43 percent of the vote in Democratic primaries across the country, motivated millions of young people to engage in politics, shook up (and angered) the party’s establishment, and, astonishingly enough, was transformed at an advanced age into a gruff, white-haired political rock star who now requires, as in his home state, no other identification than a single name — an exalted status reserved for a relative few in all fields of endeavor.

There’s evidence that since then, the Sanders insurgency has successfully channeled the mainstream of the Democratic Party to the left, as he continues to travel the country to stump for progressive candidates and push for progressive causes. His policy prescriptions have also gained wider acceptance in party circles, including Medicare for all, a $15 minimum wage and free tuition at public colleges and universities. And his supporters are pushing hard to open up the nominating process next time.

Many expect that Sanders’ re-election effort, if successful, will be a prelude to another presidential campaign. It may well be. But there are obstacles. There’s age, for one thing, in light of the enormous stamina required to make a serious run for president. It’s unclear whether supporters of Hillary Clinton can or want to overcome the hard feelings engendered by his primary challenge in 2016. The Politico website reported recently that the grass-roots organization he inspired, Our Revolution, is in disarray. Although he has no formal affiliation with it, some supporters think that if Our Revolution struggles, it will have a negative effect on a future Sanders’ national campaign.

On the other hand, by 2020, Sanders’ longstanding, honorable and, yes, genuine concern for the struggles of ordinary Americans may stand in stark and welcome contrast for many voters to the authoritarian grandstanding of President Trump, who with each passing week increasingly sacrifices the interests of his populist base to the slimy inhabitants of the swamp he famously vowed to drain.

But even if not, history says that you can depend on Sanders to keep on fighting the good fight, in his own inimitable and slightly grumpy fashion.