Donald Trump's top aides have said the US president-elect is not ready to accept the finding by intelligence officials that Moscow hacked Democratic emails in a bid to elevate the billionaire property mogul.
And they stressed that even if it were true, Republican Mr Trump still won the White House fair and square.
Meanwhile, members of the Electoral College will formally cast votes for Mr Trump as the nation's 45th president on Monday.
While Democrats are probably powerless to stop it, they suggested Mr Trump's victory over Democrat Hillary Clinton would forever be tainted by Russian meddling.
Republican electors have been inundated by Trump opponents urging them to defy the results in their states and vote against him.
"This whole thing is a spin job," said Mr Trump's incoming chief of staff Reince Priebus. "And I think what the Democrats ought to do is look in the mirror and face the reality that they lost the election."
Trump himself weighed in Sunday evening, tweeting, "If my many supporters acted and threatened people like those who lost the election are doing, they would be scorned & called terrible names!"
If my many supporters acted and threatened people like those who lost the election are doing, they would be scorned & called terrible names!— Donald J. Trump (@realDonaldTrump) December 18, 2016
The partisan swipes mostly ignored warnings by foreign policy experts that part of Russia's calculation also was probably payback for years of US criticism of its own elections and a desire to portray America as a flawed champion of democracy - potentially weakening US power on the world stage.
Russia has vehemently denied the accusation.
Many politicians, including some leading Republicans, say voters may not have been swayed by the release of tens of thousands of private emails. But the fact that a foreign power tried to intervene in US democracy and exploit divisions in American politics is cause for alarm, they say.
Still, Mr Trump's transition team and loyalists on Capitol Hill were not buying it, at least not on the eve of the Electoral College vote.
"Where's the evidence?" said Kellyanne Conway, another close Trump adviser.
Asked about President Barack Obama's vow to retaliate against the Russians, she said: "It seems like the president is under pressure from Team Hillary, who can't accept the election results."
Democrats say it is unlikely the public will ever hear detailed evidence because doing so would disclose classified sources and methods. But with last week's declaration by CIA director John Brennan that there was "strong consensus" that Russia hacked Democrats to try to sway the election, politicians are stepping up demands for closed-door briefings and a separate congressional investigation.
California congressman Adam Schiff, the senior Democrat on the House of Representatives Intelligence Committee, said an unclassified intelligence review could be released within the next two or three weeks.
As president-elect, Mr Trump would have access to high-level intelligence on the matter, although it is unclear what he has been told. He has previously called the intelligence finding of Russian involvement "ridiculous".
On Sunday, Ms Conway said she was not privy to the same intelligence briefings as the president-elect and could not say what he knows.
Donna Brazile, interim head of the Democratic National Committee, said the DNC was no match for a sophisticated foreign power in cyberspace that "weaponised" private emails to "sow misinformation and to sow discord" between Mrs Clinton and her primary rival, Vermont senator Bernie Sanders.
Ms Brazile said the cyber attacks against the DNC occurred every day through the end of the election - a comment that seemed to contradict Mr Obama's assertion that they stopped after he warned Russian president Vladimir Putin in September.
Democrat senator Chuck Schumer and Republican counterpart John McCain, meanwhile, have called for the creation of a Senate investigative committee focused on Russia, China and Iran potentially trying to interfere in US elections through high-tech meddling.