President Trump prepares to board Marine One en route to his Mar-a-Lago estate in Palm Beach, Fla., following the release of the Mueller report April 18. (Carlos Barria/Reuters)

The report from special counsel Robert S. Mueller III lays out in stark detail Russian efforts to foment anger in the U.S. electorate and influence the 2016 election. But it also makes clear the extent to which that 2016 Russian campaign has indelibly formed the landscape for the 2020 race.

On the campaign trail, President Trump and his supporters still rail regularly about the need to investigate Hillary Clinton and her missing emails. Calls to “lock her up” are a part of many rallies. 

On the Democratic side, old grudges laid bare by the Russian hacks and disinformation campaign are a significant part the 2020 battlefield. Supporters of Sen. Bernie Sanders (I-Vt.) still regularly cite emails purloined by the Russians to argue that the nomination was stolen from him. Some insist, incorrectly, that Sanders received more votes than Clinton.

Earlier this week, Sanders added to that sense of grievance, accusing a liberal think tank of trying to undermine his 2020 presidential campaign. “The Democratic primary must be a campaign of ideas, not of bad-faith smears,” Sanders wrote in a letter to the board of the Center for American Progress (CAP).

The bad blood between Sanders and CAP traces back to Russia’s 2016 hack of emails from the Democratic Party and Clinton’s campaign chairman, John Podesta. Sanders was upset that CAP “fought” him on a $15 minimum wage and other policies, said Faiz Shakir, Sanders’s campaign manager. His evidence: A hacked email from CAP President Neera Tanden disparaging the idea.

At its outset, the Russian effort sought to sow “discord in the U.S. political system,” according to the Mueller report. That discord and lack of trust, in turn, made Americans more vulnerable to the Russian disinformation efforts that followed. 

Over time the disinformation and hacking campaign, which began in 2014, evolved to support Trump and disparage Clinton. Internal documents from the Russia-based Internet Research Agency cited directions to IRA operators not to harm Sanders.

“Main idea: Use any opportunity to criticize Hillary [Clinton] and the rest (except Sanders and Trump — we support them)” the report quoted an IRA document as stating. Sanders’s 2016 campaign manager, Jeff Weaver, said recently that “none of us knew” about the Russian interference.

Now, some 30 months after the 2016 election, the U.S. government and its biggest tech companies are better positioned to identify Russian interference. The FBI has a foreign influence task force and many technology companies have disinformation units aimed at thwarting foreign influence. The biggest companies, such as Google, Twitter and Facebook, gather intelligence about disinformation efforts, shut down problematic accounts and require a new degree of transparency and verification when customers buy political ads.

“One of the biggest problems was a lack of cooperation between the public and private sectors in 2016,” said Alex Stamos, former chief security officer at Facebook and now director of the Stanford Internet Observatory. “It was nobody’s job.”

But so many of the conditions that made the U.S. electorate vulnerable to Russian hacking — polarization, anger, lack of trust in U.S. institutions — have grown significantly worse in the years since 2016.

“I’m going to keep repeating this point: Our vulnerability to Russia or any other foreign power is directly related to how divided, partisan and dysfunctional our political process is,” then-President Barack Obama told reporters weeks after the 2016 election. “So if we really want to reduce foreign influence . . . then we better think about how to make sure our political process . . . is stronger than it has ever been.”

By almost every measure, the partisan discord that marked 2016 has only grown worse, between the political parties and inside them.

Trump’s relentless attacks on the news media as the “enemy of the people” have dramatically widened the gap between Republican and Democratic perceptions of the news media’s accuracy and trustworthiness, according to surveys by the Pew Research Center. In 2016 similar numbers of Republican and Democrats said they believed the national news media “do very well” at keeping them informed. By 2018 the gap between Democrats and Republicans was 16 percentage points.

The president also has worked to diminish other institutions, including the courts, the Justice Department and federal agencies.

On matters of policy, the views of most Americans haven’t changed substantially. But the vehemence of their positions has. “What has changed is that partisans report disliking the other party more than they did a few years ago, continuing a long trend of growing animosity,” said Nathan Kalmoe, a political scientist at Louisiana State University. “The us versus them aspect of partisanship has gotten worse.”

Another factor likely to influence the 2020 campaign: The Russians have become more adept at using social media to manipulate public opinion.

The Mueller report documents Russian trolls with tens of thousands of followers on Twitter and Facebook. And it offers repeated instances of their social media messages being touted in the news media and by top Trump campaign officials, including the president, who as recently as September 2017 responded to a “We Love You, Mr. President” tweet from @10_GOP, a Russian controlled account.

Even today, Russian Facebook posts and tweets can wrack up hundreds of thousands of likes and regularly find their way into real news, said Darren Linvill, an associate professor of communications at Clemson University who studies Russian disinformation efforts. “They have gotten so good at viral content,” Linvill said, “and they know where to find it.” 

Many of the most recent posts seem designed to stoke racial animosity ahead of the 2020 presidential campaign. Just last week a Russian Twitter account drew more than 33,000 retweets for a video of a white woman in Dallas threatening to call Immigration and Customs Enforcement on a taco truck.

After an online poll, the Russian troll account dubbed the woman “Taco Truck Tammy,” a moniker picked up by newspaper and television stations. Earlier this week Twitter shut down the account @Dany_xoo after Linvill called it to the company’s attention.

In the case of the 2016 hack of Democratic Party emails, the Mueller report revealed messages between Russian military intelligence and WikiLeaks laying out the two groups’ goals. “We think trump has only a 25 percent chance of winning against hillary,” a WikiLeaks message read. “so conflict between bernie and hillary is interesting.”

Now, that conflict is playing out in the context of 2020 and a crowded and competitive Democratic field.

“The dangers on the Democratic side are much deeper than they were,” said Stamos, the former Facebook security chief. “The large number of candidates and leftover ill feelings from 2016 increase the likelihood that some Democratic voters will emerge from the primary process disaffected.”

“If I was working at a Russian troll farm . . . I would be 100 percent focused on the Democratic primary,” Stamos said.

Democratic officials are doing their best to safeguard against such efforts by encouraging candidates to work together to battle trolls and disavow information gleaned through illegal hacks.

“Like you, we don’t want a repeat of what happened in 2016, and are alarmed by recent reports of ongoing activity by hostile foreign powers and malicious domestic actors,” a recent letter from Association of State Democratic Committees to its state chapters says. The letter proposes discussions with the presidential primary campaigns and the Democratic National Committee to agree to a “new set of norms” for this “age of social media and disinformation.”

But some experts are skeptical that these new efforts will amount to much at a moment when voters are angry and U.S. political actors have become more adept at manipulating voter distrust.

Several liberal operatives mimicked Russians tactics in seeking to manipulate Alabama voters through social media during the 2017 special election for U.S. Senate, under the code name  Project Birmingham. Many disinformation experts now regard such threats from domestic political activists as more serious — and harder to combat — than ones from foreign operatives such as the Russians.

“They set off the powder keg, and we’ll never be able to come together in one reality again,” said Clinton Watts, a former FBI agent who studies Russian disinformation for the Foreign Policy Research Institute. “Their work is done. We’re already at each other’s throats.”

Sean Sullivan contributed to this report.