WASHINGTON — In the Obama administration’s last days, some White House officials scrambled to spread information about Russian efforts to undermine the presidential election — and about possible contacts between associates of President-elect Donald J. Trump and Russians — across the government. Former American officials say they had two aims: to ensure that such meddling isn’t duplicated in future American or European elections, and to leave a clear trail of intelligence for government investigators.
American allies, including the British and the Dutch, had provided information describing meetings in European cities between Russian officials — and others close to Russia’s president, Vladimir V. Putin — and associates of President-elect Trump, according to three former American officials who requested anonymity in discussing classified intelligence.
Separately, American intelligence agencies had intercepted communications of Russian officials, some of them within the Kremlin, discussing contacts with Trump associates.
The disclosures about the contacts came as new questions were raised about Attorney General Jeff Sessions’s ties to the Russians. According to a former senior American official, he met with the Russian ambassador, Sergey I. Kislyak, twice in the past year. The details of the meetings were not clear, but the contact appeared to contradict testimony Mr. Sessions provided Congress during his confirmation hearing in January when he said he “did not have communications with the Russians.”
Mr. Sessions said in a statement late Wednesday that he “never met with any Russian officials to discuss issues of the campaign.”
“I have no idea what this allegation is about,” he said. “It is false.”
Mr. Trump has denied that his campaign had any contact with Russian officials, and at one point he openly suggested that American spy agencies had cooked up intelligence suggesting that the Russian government had tried to meddle in the presidential election. Mr. Trump has accused the Obama administration of hyping the Russia story line as a way to discredit his new administration.
At the Obama White House, Mr. Trump’s statements stoked fears among some that intelligence could be covered up or destroyed — or its sources exposed — once power changed hands. What followed was a push to preserve the intelligence that underscored the deep anxiety with which the White House and American intelligence agencies had come to view the threat from Moscow.
It also reflected the suspicion among many in the Obama White House that the Trump campaign might have colluded with Russia on election email hacks — a suspicion that American officials say has not been confirmed. Former senior Obama administration officials said that none of the efforts were directed by Mr. Obama.
Sean Spicer, the Trump White House spokesman, said, “The only new piece of information that has come to light is that political appointees in the Obama administration have sought to create a false narrative to make an excuse for their own defeat in the election.” He added, “There continues to be no there, there.”
As Inauguration Day approached, Obama White House officials grew convinced that the intelligence was damning and that they needed to ensure that as many people as possible inside government could see it, even if people without security clearances could not. Some officials began asking specific questions at intelligence briefings, knowing the answers would be archived and could be easily unearthed by investigators — including the Senate Intelligence Committee, which in early January announced an inquiry into Russian efforts to influence the election.
At intelligence agencies, there was a push to process as much raw intelligence as possible into analyses, and to keep the reports at a relatively low classification level to ensure as wide a readership as possible across the government — and, in some cases, among European allies. This allowed the upload of as much intelligence as possible to Intellipedia, a secret wiki used by American analysts to share information.
There was also an effort to pass reports and other sensitive materials to Congress. In one instance, the State Department sent a cache of documents marked “secret” to Senator Benjamin Cardin of Maryland days before the Jan. 20 inauguration. The documents, detailing Russian efforts to intervene in elections worldwide, were sent in response to a request from Mr. Cardin, the top Democrat on the Foreign Relations Committee, and were shared with Republicans on the panel.
“This situation was serious, as is evident by President Obama’s call for a review — and as is evident by the United States response,” said Eric Schultz, a spokesman for Mr. Obama. “When the intelligence community does that type of comprehensive review, it is standard practice that a significant amount of information would be compiled and documented.”
The opposite happened with the most sensitive intelligence, including the names of sources and the identities of foreigners who were regularly monitored. Officials tightened the already small number of people who could access that information. They knew the information could not be kept from the new president or his top advisers, but wanted to narrow the number of people who might see the information, officials said.
More than a half-dozen current and former officials described various aspects of the effort to preserve and distribute the intelligence, and some said they were speaking to draw attention to the material and ensure proper investigation by Congress. All spoke on the condition of anonymity because they were discussing classified information, nearly all of which remains secret, making an independent public assessment of the competing Obama and Trump administration claims impossible.
The F.B.I. is conducting a wide-ranging counterintelligence investigation into Russia’s meddling in the election, and is examining alleged links between Mr. Trump’s associates and the Russian government. Separately, the House and Senate intelligence committees are conducting their own investigations, though they must rely on information collected by the F.B.I. and intelligence agencies.
On Wednesday, a Justice Department official confirmed that Mr. Sessions had two conversations with Ambassador Kislyak last year, when he was still a senator, despite testifying at his Jan. 10 confirmation hearing that he had no contact with the Russians. At that hearing, Mr. Sessions was asked what he would do if it turned out to be true that anyone affiliated with the Trump team had communicated with the Russian government in the course of the campaign. He said he was “not aware of any of those activities.”
“I have been called a surrogate at a time or two in that campaign and I didn’t have — did not have communications with the Russians, and I’m unable to comment on it,” Mr. Sessions said at the time.
However, Justice officials acknowledged that Mr. Sessions had spoken with Mr. Kislyak twice: once, among a group of ambassadors who approached him at a Heritage Foundation event during the Republican National Convention in Cleveland in July and, separately, in an office meeting on Sept. 8. The contacts were first reported by The Washington Post.
Sarah Isgur Flores, Mr. Sessions’s spokeswoman, said “there was absolutely nothing misleading about his answer” because he did not communicate with the ambassador in his capacity as a Trump campaign surrogate. She said Mr. Sessions had at least 25 conversations in 2016 with ambassadors from a range of nations — including Britain, Japan, China, Germany and Russia — while on the Senate Armed Services Committee.
The revelation prompted congressional Democrats to issue a torrent of statements reiterating their demands that Mr. Sessions recuse himself from overseeing any investigation into Russia’s contacts with the Trump campaign. So far, Mr. Sessions has demurred.
Representative Adam B. Schiff, the ranking Democrat on the House Intelligence Committee, said in a statement on Wednesday that if the reports about Mr. Sessions were accurate, “it is essential that he recuse himself from any role in the investigation of Trump campaign ties to the Russians.” Mr. Schiff added, “This is not even a close call; it is a must.”
Representative Nancy Pelosi, the Democratic leader of the House, called on Mr. Sessions to resign, saying on Twitter that “he is not fit to serve as the top law enforcement officer of our country.”
A White House official, speaking on the condition of anonymity, backed up Mr. Sessions late Wednesday, calling the accusations “the latest attack against the Trump administration by partisan Democrats.”
At a CNN town hall on Wednesday, Senator Lindsey Graham, Republican of South Carolina, said he did not know if there was anything between the Trump campaign and the Russians. But he added that if there was, “it is clear to me that Jeff Sessions, who is my dear friend, cannot make this decision about Trump.”
At his confirmation hearing on Wednesday, former Senator Dan Coats, Mr. Trump’s nominee for director of national intelligence, told the Senate Intelligence Committee that “I think it’s our responsibility to provide you access to all that you need.”
Some Obama White House officials had little faith that a Trump administration would make good on such pledges, and the efforts to preserve the intelligence continued until the administration’s final hours. This was partly because intelligence was still being collected and analyzed, but it also reflected the sentiment among many administration officials that they had not recognized the scale of the Russian campaign until it was too late.
The warning signs had been building throughout the summer, but were far from clear. As WikiLeaks was pushing out emails stolen from the Democratic National Committee through online publication, American intelligence began picking up conversations in which Russian officials were discussing contacts with Trump associates, and European allies were starting to pass along information about people close to Mr. Trump meeting with Russians in the Netherlands, Britain and other countries.
But what was going on in the meetings was unclear to the officials, and the intercepted communications did little to clarify matters — the Russians, it appeared, were arguing about how far to go in interfering in the presidential election. What intensified the alarm at the Obama White House was a campaign of cyberattacks on state electoral systems in September, which led the administration to deliver a public accusation against the Russians in October.
But it wasn’t until after the election, and after more intelligence had come in, that the administration began to grasp the scope of the suspected tampering and concluded that one goal of the campaign was to help tip the election in Mr. Trump’s favor. In early December, Mr. Obama ordered the intelligence community to conduct a full assessment of the Russian campaign.
In the weeks before the assessment was released in January, the intelligence community combed through databases for an array of communications and other information — some of which was months old by then — and began producing reports that showed there were contacts during the campaign between Trump associates and Russian officials.
The nature of the contacts remains unknown. Several of Mr. Trump’s associates have done business in Russia, and it is unclear if any of the contacts were related to business dealings.
The New York Times, citing four current and former officials, reported last month that the American authorities had obtained information of repeated contacts between Mr. Trump’s associates and senior Russian intelligence officials. The White House has dismissed the story as false.
Since the Feb. 14 article appeared, more than a half-dozen officials have confirmed contacts of various kinds between Russians and Trump associates. The label “intelligence official” is not always cleanly applied in Russia, where ex-spies, oligarchs and government officials often report back to the intelligence services and elsewhere in the Kremlin.
Steven L. Hall, the former head of Russia operations at the C.I.A., said that Mr. Putin was surrounded by a cast of characters, and that it was “fair to say that a good number of them come from an intelligence or security background. Once an intel guy, always an intel guy in Russia.”
The concerns about the contacts were cemented by a series of phone calls between Mr. Kislyak and Michael T. Flynn, who had been poised to become Mr. Trump’s national security adviser. The calls began on Dec. 29, shortly after Mr. Kislyak was summoned to the State Department and informed that, in retaliation for Russian election meddling, the United States was expelling 35 suspected Russian intelligence operatives and imposing other sanctions. Mr. Kislyak was irate and threatened a forceful Russia response, according to people familiar with the exchange.
But a day later, Mr. Putin said his government would not retaliate, prompting a Twitter post from Mr. Trump praising the Russian president — and puzzling Obama White House officials.
On Jan. 2, administration officials learned that Mr. Kislyak — after leaving the State Department meeting — called Mr. Flynn, and that the two talked multiple times in the 36 hours that followed. American intelligence agencies routinely wiretap the phones of Russian diplomats, and transcripts of the calls showed that Mr. Flynn urged the Russians not to respond, saying relations would improve once Mr. Trump was in office, according to multiple current and former officials.
Beyond leaving a trail for investigators, the Obama administration also wanted to help European allies combat a threat that had caught the United States off guard. American intelligence agencies made it clear in the declassified version of the intelligence assessment released in January that they believed Russia intended to use its attacks on the United States as a template for more meddling. “We assess Moscow will apply lessons learned,” the report said, “to future influence efforts worldwide, including against U.S. allies.”