WASHINGTON — President Trump attacked a leading House Democrat on Tuesday over upcoming classified intelligence briefings by members of his own administration on the issue of election interference, suggesting his political opponents were exaggerating the threat from Russia.
Mr. Trump has previously issued derogatory statements about his intelligence chiefs after congressional hearings, but even before Tuesday’s briefings, he posted on Twitter that he “wouldn’t expect too much.”
Mr. Trump incorrectly said the first of two briefings, to House members, would be led by Representative Adam B. Schiff, Democrat of California and chairman of the House Intelligence Committee. The briefing on Tuesday was arranged by Speaker Nancy Pelosi, not Mr. Schiff. The Senate will receive an identical briefing later Tuesday afternoon.
Mr. Schiff fired back, noting that the officials briefing lawmakers were the president’s “own people” including several agency heads.
“We will insist on the truth, whether you like it or not,” Mr. Schiff said on Twitter.
Mr. Trump’s tweet showed his frustration over lawmakers’ continued concern that Russia is mounting efforts to influence the 2020 election. Mr. Trump has nurtured a grudge against Mr. Schiff since he took a leading role investigating ties between Mr. Trump’s campaign and Russia, and his leadership of the impeachment trial reignited the president’s ire.
Since his election, Mr. Trump has tried to play down or even dismiss discussions about Russia’s interference campaigns, chafing at the prospect that he won with the help of a foreign power. Some officials have said that they worry that the president’s dismissive comments make it harder for intelligence agencies and officials with the Department of Homeland Security to counter Moscow’s covert operations to influence the presidential election in November.
Russia has stepped up those efforts, officials have said, exploiting existing divisions among Americans to sow chaos. In particularly, Kremlin intelligence operatives have sought to amplify the messages of white supremacist groups to try to incite violence.
Senator Mitch McConnell, Republican of Kentucky and the majority leader, sounded a far different tone than the president, urging senators of both parties to attend what he called a discussion on a “critical subject.” Though he also addressed Democrats’ intense focus on Russia — the briefings are to address election security threats from a variety of adversaries, including China and Iran — he offered a more neutral encouragement for lawmakers to set aside “reflexive” partisanship.
“I encourage all my colleagues to attend the bipartisan briefing today,” he said. “And then let’s preserve that bipartisan spirit and that unity. Let’s focus on fighting against foreign interference, not fighting each other.”
The classified briefings on Tuesday are some of the first on election security since a contentious closed-door briefing last month to the House Intelligence Committee. Shelby Pierson, the nation’s election security czar, discussed Russia’s preference for Mr. Trump’s re-election and its interference efforts, prompting angry responses from House Republicans.
Ms. Pierson will not attend Tuesday’s briefing, nor will her boss, Richard Grenell, the acting director of national intelligence. Congress was never told that Mr. Grenell was planning to attend the briefing, said Maura Beard, a spokeswoman for the office.
Other officials set to attend Tuesday’s briefings included: Chad Wolf, the acting homeland security secretary; Christopher A. Wray, the F.B.I. director; Gen. Paul M. Nakasone, the director of the National Security Agency; and William R. Evanina, the director of the National Counterintelligence and Security Center. Mr. Evanina will represent the Office of the Director of National Intelligence, Ms. Beard said.
The briefings are classified, but administration officials are not expected to discuss the most sensitive intelligence in front of such a large audience. They will also be seeking to avoid the controversy over the February briefing with Ms. Pierson.
Nevertheless, lawmakers are expected to press the officials on Russia’s efforts in support of Mr. Trump and in support of Senator Bernie Sanders in the Democratic presidential primaries and it’s attempts to incite racial violence ahead of the fall vote.