The Vermont independent senator, who caucuses with the Democrats, is tapping back into his national network of supporters. He's drawing millions of viewers for events he streams live on Facebook. And he's delivering a series of speeches designed to counter President Donald Trump and offer his own progressive vision.

Taken together, his moves in 2018's first weeks show that Sanders is road-testing ways to deliver a message tailored to the Trump era without filters, and to activate his supporters behind it -- even as he insists publicly and privately that it's too early to commit to a 2020 presidential run.

"We are starting to see the beginning of a political revolution, something long overdue," Sanders declared after scanning the progressive anti-Trump resistance in his live-to-Facebook response to Trump's State of the Union this week.

There is ample reason to doubt a Sanders 2020 run: He'd be 79 years old on election day. His wife, Jane Sanders, is embroiled in a federal investigation into a land deal she made while president of Burlington College. And an awkward clash with a local newspaper reporter showed that Sanders may be uncomfortable entering the race as a front-runner, where the scrutiny is more intense and impossible to control.

But the next presidential race is on the minds of Sanders' allies. A number of top aides involved in his 2016 campaign huddled recently and discussed what a 2020 presidential run would look like -- a meeting first reported by Politico

Still, Sanders' camp insists he's focused now on helping Democrats -- particularly like-minded progressives -- win this year, in hopes of stymieing Trump for the latter half of his first term.

"That's really where his head is at, is 'How do we put a check on the President?'" said Jeff Weaver, Sanders' 2016 campaign manager. "For everybody who is horrified about what this White House is trying to do, having a Democratic-controlled Congress -- even one house of Congress -- would be a tremendous check."

2018 plans

Sanders intends to travel extensively to support progressive candidates. First up, aides said, is likely a Midwestern trip where Sanders would campaign for three Democratic House contenders: Chuy Garcia in Illinois, Sanders presidential campaign veteran Pete D'Alessandro in Iowa and Randy Bryce, who is challenging House Speaker Paul Ryan in Wisconsin.

For the midterms, Sanders also plans to re-activate his "distributed organizing network" of supporters -- the massive network of volunteers who made tens of millions of calls and texts for his presidential campaign -- to help Democrats Sanders supports.

Such a trial run would be a luxury if he were to run for president in 2020. Sanders' 2016 campaign started as a shoestring operation and expanded on the fly as he gained momentum; he'd enter 2020 with an infrastructure and network far larger than those of any other Democrat, and with many of the kinks already worked out.

Bernie TV

Since the 2016 election, Sanders has also built a massive collection of Facebook videos -- and is now beginning to host his own live events, circumventing the mainstream political press while attracting massive audiences.

Most clips are short -- between one and three minutes. His staff posts as many as five videos a day -- often just packaging, adding context and slapping a logo onto Sanders' remarks in TV interviews or at public events. Sanders brought on NowThis News' Armand Aviram to help produce them. And, spokesman Josh Miller-Lewis said, the senator personally weighs in on the videos' content "all the time. It's one of his biggest areas of focus."

The short videos are posted on his Senate Facebook page, which has 7.5 million followers. (His campaign page has another 5 million.)

They get attention -- combined, his "Medicare for all"-focused videos have more than 100 million views since August.

But the biggest events are Sanders' livestreams. He drew 1.1 million live viewers for a "Medicare for all" town hall in January -- an evening audience that rivaled cable news networks -- and 2 million viewers total. His State of the Union response got 1 million total viewers.

Sanders has partnered with progressive online news outlets to air his events. He's also launched his own podcast.

Big speeches

He's also making sweeping speeches focused on topics far removed from Trump-focused news cycles. On Wednesday, Sanders delivered a speech focused on climate change -- a notable omission in both Trump's State of the Union and Massachusetts Rep. Joe Kennedy III's official Democratic response.

But while Sanders is most comfortable talking about his bread-and-butter issues -- Medicare for all, climate change, college affordability and income inequality -- he's also taking Trump on in cultural terms.

At a Latino Victory Fund event this week, Sanders labeled the Trump White House "the most extremist, reactionary, xenophobic, bigoted and thankfully, in many ways, the most inept and incompetent administration in the history of our country."

"What Trump and his friends are trying to do is exploit old fracture lines in our society -- racism, sexism, homophobia, Islamophobia, religious bigotry," he said. "In these dismal times, it is more important now than ever that we offer a vision to the American people -- a vision of hope; a vision of what this nation can become."