A congressional intelligence panel so far has found "no evidence" that Donald Trump's campaign colluded with Russia during the 2016 election, its chairman said Sunday, ahead of testimony by the head of the FBI on the US president's potential Russia ties.
Based on "everything I have up to this morning -- no evidence of collusion," by Trump's team and Moscow, Representative Devin Nunes, chairman of the House Intelligence Committee, told Fox News.
Nunes made his remarks one day before Federal Bureau of Investigation Director James Comey is to face lawmakers on the panel, amid speculation that Trump aides and associates -- and perhaps even the businessman-turned-politician himself -- may have had uncomfortably close ties with Moscow.
Monday's hearing was also expected to address a second explosive issue: Trump's unsubstantiated accusations of wiretapping by Barack Obama -- charges that have roiled political waters in Washington for the past two weeks.
Trump on March 4 tweeted that Obama had "tapped" his phone -- a charge that has consumed political debate in the US capital.
The US intelligence community has publicly blamed Russia for hacks of the Democratic National Committee last year, and suggested the cyber attacks were aimed at steering the election to a Trump victory.
Russia has denied involvement in the hacks, and Trump has denounced the tumult over the Russia connections as a "total witch hunt."
WATCH: Tensions show as Trump, Merkel meet for the first time
Washington obsesses over baseless wiretap claim
But the question of whether Trump Tower was bugged -- an accusation first lodged by the president on Twitter -- nevertheless has risen to the top of Washington's political agenda, becoming something of a national obsession even as a growing number of lawmakers and top US officials assert there is no evidence of any such claim.
The wiretapping issue mushroomed last month, when Trump's national security adviser Michael Flynn was forced to resign after it was revealed he had misled top officials over his contacts with Russia.
Around the same time, The New York Times reported that US intelligence agents had intercepted calls showing that members of Trump's campaign had repeated contacts with top Russian intelligence officials in the year preceding the November 8 election.
Nunes has said that the intelligence committee probe focuses in part on who revealed the fact that Flynn had unreported private contacts with the Russians over the issue of international sanctions against Moscow -- a disclosure which led to his forced resignation as Trump's national security adviser.
Adding to the intrigue, Trump's attorney general Jeff Sessions had to recuse himself from any Russia-related inquiries after it was learned that he had met twice with the Russian ambassador in the months before Trump took office, and had failed to disclose this during his confirmation hearing.
Trump's credibility takes a hit
Domestically, the headline-grabbing controversy over the wiretapping claim has pulled attention away from Trump's effort to push through other key items on his agenda, including the planned repeal of Obama's healthcare law, tax reform and his controversial travel ban.
Critics say it has also debased the already-coarse tone of political debate in Washington and eroded the president's credibility at home and abroad.
Some of the fallout has been international in scope: The White House was forced to retract a charge repeated last week by its spokesman Sean Spicer suggesting that Britain's intelligence services aided the Obama administration in the alleged wiretap. That claim has strained relations with America's closest ally.
Still, as recently as Friday, Trump repeated the baseless claim in an aside during a White House press conference with Angela Merkel.
"As far as wiretapping, I guess, by this past administration, at least we have something in common, perhaps," Trump told the German chancellor, referring to a WikiLeaks report in 2015 that the US had monitored calls involving Merkel and her top aides for years.
Republican Senator Ted Cruz -- Trump's vanquished rival last year for the Republican presidential nomination -- said the wiretapping charges are not entirely "outlandish" and should be investigated.
'Not necessarily outlandish'
"I think it would be quite good for the administration to put forward what evidence there is," Cruz told CBS television.
"You know, I will point out this is not necessarily as outlandish as everyone in the press suggests. We do know that the Obama administration targeted their political enemies... so the notion is not necessarily outlandish, but it's serious," he said.
With the national debate consumed by talk over Trump's wiretapping claim, one US lawmaker said the president might be well advised to follow the sage parental counsel he received years ago.
"To quote my 85-year-old father... 'It never hurts to say you're sorry,'" Representative Will Hurd, a Republican from Texas, told ABC television.
"And it's not just sorry to (Obama) but sorry to the (United Kingdom) for the claims -- or the intimation -- that the U.K. was involved in this as well," said Hurd, himself a former intelligence agent.