Updated at 9:40 a.m. ET

Four years after Russian election interference rattled and embarrassed national Democrats, the party has gone on offense over what it fears are more schemes targeting this year's presidential race.

Democratic leaders in the House and Senate this week demanded an all-lawmaker briefing from the FBI about what they suspect are active efforts aimed at Congress. Former Vice President Joe Biden, the party's likely presidential nominee, followed up on Wednesday with a more specific gambit.

Biden's campaign said that Sen. Ron Johnson, R-Wis., chairman of the Senate Homeland Security Committee, could be at the receiving end of a pipeline of disinformation that originates in Russia.

Johnson and his committee have said they're continuing to investigate the work Biden's son Hunter did in Ukraine while Biden was the point man on the country's new government for the Obama administration.

The storyline that a Ukrainian company was paying Hunter Biden in hopes that he could open doors in Washington has chastened the elder Biden, even back in 2014, but investigators in Ukraine have concluded no laws were broken.

Johnson and the Homeland Security Committee are still gathering material and interviewing witnesses with the aim of hearings or other activity targeting the Bidens — and Democrats worry that some of what they reel in could be fabricated or manipulated with the goal of hurting Biden and interfering in the 2020 election.

Biden spokesman Andrew Bates cited what he called evasive answers or silence from Johnson and his staff about the Ukraine work.

"Senator Johnson is not only diverting the Senate Homeland Security and Governmental Affairs Committee away from oversight of Donald Trump's failed response to the coronavirus outbreak ... not only engaged in total hypocrisy by virtue of his years-long support for the anti-corruption victory Vice President Biden delivered in Ukraine, and not only advancing the interests of Russia in a manner that is openly distressing to his Republican colleagues — but he has also revealed his complicity in a foreign attack on the very sovereignty of our elections."

Austin Altenburg, a spokesman for Johnson and the Homeland Security Committee, rejected Biden's allegations.

"The Democrat and Ukrainian claims are false, and the Democrats know this," he said.

Altenburg declined to comment on the committee's ongoing investigation or its interviews with potential witnesses, but he noted that Johnson has joined with the Democratic leaders who asked for more information from the FBI this week about the prospect of a disinformation scheme.

"Committee staff has already requested and received a staff briefing on this issue, and Chairman Johnson has requested an additional briefing at the member level," he said. "That briefing has not occurred in part because the agencies requested additional information from minority staff, which has not followed on these requests since mid-May."

New rules in the ballgame

This week's back-and-forth underscored just how deeply and how frequently the prospect of foreign interference — never absent in U.S. politics but also seldom top of mind for those involved before this era — has come to dominate the daily work of politics.

Biden's charge against Johnson followed an earlier allegation against One America News,a cable news network friendly to President Trump, which Biden's camp suspected also might be in receipt of suspicious material connected to the Ukraine storyline.

Meanwhile, Trump and Attorney General William Barr have suggested, without any public evidence, that a foreign nation might exploit increased voting by mail this year to manipulate the results of the election. Specialists say that would be practically impossible, but the threat and the discussion now are part of the political tradespace. As he did in 2016, Trump often warns about the potential for what he calls an unfair election.

Foreign interference specialists use many tools and techniques, U.S. investigators have found, including stealing confidential material and releasing it to embarrass their targets; attempting to compromise elections infrastructure with cyberattacks; and amplifying discord and spreading disinformation online.

In the past, they've also fabricated evidence to sow doubt about the inner workings of political life, including in chapters about which little remains confirmed. In one example in 2016, U.S. intelligence investigators apparently suspected that Russian specialists had created a fake evidentiary trail tying then-Attorney General Loretta Lynch to false assurances made to Hillary Clinton's campaign about the FBI email investigation.

The full story remains unknown; in his memoir, former FBI Director James Comey alluded to the anecdote but said it remained too secret for him to reveal in detail.

This opacity creates an opportunity — and dilemma — for politicians wielding election interference as an issue. The fundamental intelligence about what American spies are hearing and learning seldom becomes public. And the reports that do make their way to members of Congress and administration officials evidently are worded so carefully that everyone involved feels entitled to draw separate conclusions.

What Democrats heard in a briefing earlier this year was that the intelligence community has assessed that Russia wants to support Trump over Biden in the 2020 race, as it supported him over Clinton. But that conclusion angered Republicans, who didn't hear such certainty; national security adviser Robert O'Brien said he hadn't seen any such evidence.

The broad facts about interference and potential vulnerabilities mostly aren't disputed, and new evidence emerges regularly about what has happened and what may be happening now, including a British study about Russian cyberattacks and subversion.

Sen. Roy Blunt, R-Mo., who chaired a hearing on Wednesday focused on the fraught, pandemic-stricken election days that remain this year, hailed what he called the progress local leaders have made on security this year even as they also figure out how to operate amid social distancing and infection.

"Election officials have done all this on top of continuing efforts to ensure that this country's elections are secure from malicious actors who seek to attack voting infrastructure and spread disinformation," Blunt said. "All of these actions have been taken to ensure that every voter can cast their ballot safely and securely in this year's election. That's something that everyone here can agree on: voters in this country must be able to cast a ballot safely and surely without putting their health at risk."

Although Blunt and some Republicans agree that more funding is in order for elections this year, Democrats argue that still more is needed — not only from Congress but at the presidential level.

Biden vowed this week that if he's elected, he'll not only focus more on election security but punish any foreign governments linked with interference.

Tony Blinken, a top foreign policy adviser to Biden, alluded specifically to Russia and President Vladimir Putin.

"The vice president put Putin and others who might seek to interfere on notice that if he's elected president, they're going to be facing something totally different than what they're dealing with now," he said. "Instead of ignoring or denying it, he will impose significant and lasting costs and consequences for meddling in our democracy."

Putin and other antagonists not only want to sow chaos but also corrode public confidence in democratic systems — regardless of which party thinks it can win the day's headlines on the latest installment in the saga, said David Shimer, a global fellow at the Woodrow Wilson Center.

"History clarifies that the threat of foreign electoral interference is a threat to our nation, not any one political party," said Shimer, author of Rigged, a recent history of modern election interference. "The Soviet Union worked on several occasions to tarnish the campaigns of Richard Nixon and Ronald Reagan, Republicans, long before Russia worked to help a Republican. Putin's objective here is to direct, disrupt, and delegitimize our process of succession, and that should alarm all Americans."

NPR political correspondent Scott Detrow contributed to this report.

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