(CNN) Bernie Sanders took his long-running fight with the Democratic Party establishment very public Friday night, hours after news broke that Russia is working to help his 2020 primary bid and hours before the critical Nevada caucuses .

"I've got news for the Republican establishment," the Vermont senator tweeted on Friday night . "I've got news for the Democratic establishment. They can't stop us."

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Whoa boy!

The timing of that tweet seems not to be an accident.

The Washington Post reported earlier Friday afternoon that the Sanders campaign had been briefed on attempts by the Russians to help his campaign, although it was not clear how that aid was manifesting itself.

Sanders confirmed Friday that he had been informed of the attempted Russian efforts a month ago. "We were told that Russia, maybe other countries, are going to get involved in this campaign, and look, here's the message to Russia: Stay out of American elections," Sanders said.

He also -- in a prelude of his tweet later Friday night -- seemed to suggest to reporters on the campaign trail that the timing of the Post's report was suspicious. He noted that the Nevada caucuses were less than a day away, then asked who reported the news. When told it was The Washington Post, Sanders said sarcastically: "Good friends." (Here's the video of the exchange.)

Later, Sanders communications director Mike Casca seemed to point the finger at the Trump administration. "If you think this leak wasn't designed to hurt Bernie, you're not paying attention," he tweeted . "it's very clear Trump is nervous about facing him in the general election."

And then, Sanders tweeted -- making very clear that he views himself as at war with the establishments of both parties. As expected, it brought a considerable, and considerably negative, response from the so-called party establishment.

"The Democratic establishment gave us civil rights, voting rights, the assault weapons ban, social security and Medicare," tweeted longtime party strategist Joe Lockhart. "What have you done Senator?"

The truth is that for as long as Sanders has been running for president -- including in the 2016 race -- there has been a not-so-secret war between the Democratic establishment and Sanders, his campaign and his supporters.

The 2016 primary election only deepened the ill will -- as hacked emails from the Democratic National Committee showed that staffers within the organization had clearly put their thumb on the scale for Hillary Clinton. Sanders eventually endorsed Clinton but the bad feelings obviously never went away.

"Nobody likes him, nobody wants to work with him, he got nothing done," Clinton said of Sanders in a documentary about the campaign, released this year. "He was a career politician. It's all just baloney and I feel so bad that people got sucked into it."

Sanders sought to downplay those Clinton attacks in January. But he clearly continued to internalize his frustrations.

And things only got worse during the Iowa caucus fiasco . Not only was the vote counting terribly delayed, but there was also a split between the popular vote, which Sanders won, and the state delegate allocation, which former South Bend, Indiana, Mayor Pete Buttigieg won.

It all played into -- in the minds of Sanders and his supporters -- the idea that something was going on. They weren't -- and aren't -- entirely sure what that something is or who is behind it, but they are certain it's there. And it's because Sanders has created a movement that isn't dependent on the party -- and, in fact, has been formed in direct opposition to the establishment.

To be clear: Sanders isn't totally wrong! There are lots and lots of longtime Democratic political professionals who believe that nominating a self-proclaimed democratic socialist is a recipe for disaster for their side.

And even Sanders' rivals for the Democratic nomination are seeking to make an issue out of his casual relationship with the party. "Let's put forth someone who is actually a Democrat," Buttigieg said in Wednesday night's debate in Las Vegas.

What Sanders' tweet Friday night will do is simply make the existing dynamic in this race much more obvious: There is Sanders and the battle to be the establishment alternative to Sanders. That's it.

Now Sanders has said it -- and thrown down the gauntlet. Can the establishment fight back and win?