Mr. Trump’s salvo punctuated an escalating war with congressional Democrats over the Russia investigations. On Wednesday morning, the president attacked Senator Dianne Feinstein, Democrat of California, for releasing a transcript that was highly critical of Mr. Trump, and he demanded that Republicans “finally take control” of the probes.
For their part, Senate Democrats released an extensive report on Russia’s interference in the 2016 presidential election, saying that it fit into a nearly two-decade pattern of meddling with governments around the world. They charged that the United States’ response to Russia’s brazen attack has been hindered by Mr. Trump.
The report is one of the most expansive to date on foreign interference by Russia and President Vladimir V. Putin. It tracks Russian efforts in 19 countries, chronicling misinformation campaigns, the funding of far-right political causes and the manipulation of energy supplies long before 2016 in an attempt to glean lessons for American officials considering how to counteract similar efforts here.
In total, the report offers more than 30 recommendations to safeguard the country’s electoral process and to work with allies, primarily in Europe, to establish new standards to address these types of threats. They include new sanctions to punish states that initiate cyberattacks on elections or critical infrastructure, an international summit meeting centered on such threats, an allied commitment of mutual defense against cyberattacks, as well as forcing social media companies to disclose the sources of funding for political ads.
But the report begins by calling on Mr. Trump to “assert presidential leadership” to establish a governmentwide response to the Russian efforts, including setting up an interagency center modeled after the National Counterterrorism Center to coordinate the American response to threats and policy related to their deterrence.
“Never before in American history has so clear a threat to national security been so clearly ignored by a U.S. president,” the report asserts.
Mr. Trump used Twitter and the news conference with Ms. Solberg to call the Russia investigations a “witch hunt.”
“There was no collusion, everybody including the Dems knows there was no collusion, & yet on and on it goes,” he wrote on Twitter. “Russia & the world is laughing at the stupidity they are witnessing.”
Senator Benjamin Cardin of Maryland, the top Democrat on the Foreign Relations Committee who commissioned the Democratic report, was no less blunt.
“While President Trump stands practically idle, Mr. Putin continues to refine his asymmetric arsenal and look for future opportunities to disrupt governance and erode support for the democratic and international institutions,” he said.
American spy agencies have concluded that Mr. Putin directed a multifaceted campaign using hacking and propaganda to try to sway the 2016 presidential election against Mr. Trump’s opponent, Hillary Clinton, and, eventually, in favor of his campaign.
Mr. Trump’s response to those findings has varied. After Congress overwhelmingly passed new sanctions in August retaliating against Russia over a range of issues including the election interference, Mr. Trump was forced to sign the measure into law in spite of his own objections. In November, after speaking with Mr. Putin, Mr. Trump said he believed that the Russian leader was sincere in his denials of interfering with the 2016 race.
On Wednesday, his wrath was aimed at Ms. Feinstein of California, the top Democrat on the Judiciary Committee, whom he called “Sneaky” for unilaterally releasing the transcript of the committee’s investigative interview with one of the founders of the firm that produced a salacious and largely unsubstantiated dossier outlining a Russian effort to aid the Trump campaign. He called her action “underhanded,” “possibly illegal” and a “disgrace.”
The new report released by Mr. Cardin does not seek to answer questions about that campaign, which is being studied closely by several congressional committees and a Justice Department special counsel, Robert S. Mueller III, but tries to put it into context. The authors argue that merely investigating the 2016 effort will be insufficient to protecting against future attacks, given the versatility and persistence of Mr. Putin’s tool kit.
Over all, the report argues that Mr. Putin’s rise and hold on power in Russia has depended on the use of force and the undermining of institutions at home and abroad. It points to successful actions taken by European nations, including Germany and Nordic countries, as models for counteracting Russian tools like disinformation and hacking.
Democrats on Capitol Hill have redoubled their efforts to draw attention to broad issues of election security and what they characterize as dangerous inaction by Republicans, who control all levels of government in Washington before this year’s midterms.
Six senior House Democrats from key committees wrote to Speaker Paul D. Ryan on Tuesday to accuse Republicans of putting Mr. Trump “ahead of our national interests” and to urge them to double down on the issue.
The Senate Intelligence Committee, one of the panels investigating the 2016 campaign, plans to release its bipartisan report on election security in the coming weeks. The committee’s investigation of what role, if any, Mr. Trump’s campaign played in the Russian effort continues, but its top members have said they felt an urgency to provide at least preliminary findings that could make a difference in political races across the country.
Some of the recommendations in Wednesday’s report mirror legislative proposals by members of both parties. Those proposals have gained little traction on Capitol Hill, and authors of those reports conceded that without backing from Mr. Trump and his party, few of the measures they outlined stood a chance of being realized.