WASHINGTON — The leaders of the Senate Intelligence Committee delivered a stark warning on Wednesday to political candidates: Expect Russian operatives to remain active and determined to again try to sow chaos in elections next month and next year.
At a rare news conference, Senators Richard M. Burr, Republican of North Carolina and the committee’s chairman, and Mark Warner, Democrat of Virginia and its vice chairman, broadly endorsed the conclusions of American spy agencies that said President Vladimir V. Putin of Russia directed a campaign of hacking and propaganda to disrupt the 2016 presidential election.
“The Russian intelligence service is determined — clever — and I recommend that every campaign and every election official take this very seriously,” Mr. Burr said.
“You can’t walk away from this and believe that Russia’s not currently active,” he added.
American intelligence agencies have concluded that Mr. Putin initially wanted to hurt Hillary Clinton’s candidacy, but later tried to explicitly help Donald J. Trump’s insurgent campaign. The senators said they have reached no conclusion on whether anyone around Mr. Trump was part of that effort.
“The issue of collusion is still open,” Mr. Burr said.
The news conference was the most extensive since the committee began its investigation of Russian meddling in the 2016 election early this year and the first time the senators have detailed so fully the trajectory of their secretive investigation and their sense of the stakes. Both men come from swing states where the presidential campaign was fought aggressively.
That appeared to have made an impression.
“There needs to be a more aggressive whole-of-government approach in terms of protecting our electoral system,” Mr. Warner said. “Remember, to make a change even in a national election doesn’t require penetration into 50 states.”
He added, “You could pick two or three states in two or three jurisdictions and alter an election.”
The Senate Intelligence Committee is one of three committees on Capitol Hill that have opened full-fledged investigations into the relationship between Mr. Trump, his associates and Russia. Given the committee’s jurisdiction over the intelligence community and a strong working relationship between Mr. Burr and Mr. Warner, it has been considered the congressional committee most likely to deliver a substantive report on Russia’s covert efforts.
Mr. Burr and Mr. Warner sought to inspire confidence on Wednesday that the committee remained on course to do so. They later got a boost from Representative Adam B. Schiff of California, the ranking Democrat on the House Intelligence Committee, who said he concurred with their statements based on his committee’s work.
The senators said that their investigators have pored over nearly 100,000 pages of classified intelligence and documents turned over by the Trump campaign and other associates of the president’s, and they have conducted more than 100 interviews with many of the top officials connected to both the Trump campaign and the intelligence community. Investigators also recently received material from Facebook and, to a lesser extent, Twitter, about advertisements on their platforms linked to Russia.
“This feels like it’s taking a long time. It is taking a long time,” Mr. Warner said. “But getting it right and getting all the facts is what we owe the American people.”
Mr. Burr had expressed a desire this summer to conclude the inquiry by year’s end. But on Wednesday, he all but conceded that with so many avenues of investigation still open — 25 interviews are scheduled for the remainder of October alone — that would not be possible. While he declined to put a date on the investigation’s conclusion, he said that the committee planned to release portions of its findings before the 2018 midterm election primaries.