More than a week after United States president Donald Trump tweeted his extraordinary, unsubstantiated wiretapping claims against Barack Obama, he is yet to provide any evidence.
Mr Trump tweeted that President Obama had Trump Tower wiretapped during the US election campaign.
Now, both Republican and Democratic leaders on the House of Representatives Intelligence Committee say there is no evidence of such wiretapping.
Democratic Congressman Adam Schiff says he thinks the White House has been trying to downplay the fact the President said something not true.
"My interpretation, frankly, of what the White House has been communicating since the President's tweets were, first, 'We don't want to talk about this, we're giving it to the Intelligence Committee,' then, 'We're not sure if there's (anything) there,' then, 'Well, maybe he meant something different,' to, 'Well, maybe it was the TV or the microwave,' to, 'No, we fully believe the President will be vindicated in his claims of wiretapping.' So they've been all over the map.* The reality is, I don't think they have the foggiest idea what was behind the President's claim except maybe something he watched on TV."
Under US law, presidents cannot direct wiretapping.
Instead, the federal government can ask a court to authorise the action, but it must provide justification.
Republican chairman Devin Nunes says Mr Trump's claim, if taken literally, is wrong.
"If the White House or the President wants to come out and clarify his statements more, it would probably ... probably be helpful. But, you know, look, at the end of the day, just like I said last week, you know, President Obama doesn't do wiretapping, just like President Trump can't do wiretapping, so just the whole premise of the ... of the statement was wrong. So then you have to figure out, 'Okay, did he actually mean it literally or did he not?' And I think that's the question that we have here."
Earlier this week, White House press secretary Sean Spicer said Mr Trump had used the word "wiretapping" when he really meant "broader surveillance activities."
Mr Spicer also claimed Mr Trump had been referring to the Obama administration broadly, not accusing Mr Obama of personal involvement.
Republican senator Lindsey Graham says he has received a note from the FBI saying he will receive a confidential briefing on wiretapping allegations.
The briefing would come before FBI director James Comey testifies at a hearing into the matter next week.
Mr Graham says the briefing is in response to a letter he sent to Mr Comey, in which he posed a question:
"Was there a warrant issued by any court anywhere in the United States allowing the surveillance of the Trump campaign, Trump Tower or any Trump operative during the 2016 election? And please provide the information that was used to obtain a warrant. If a warrant was requested and denied, we'd also like to know that."
Meanwhile, a congressional hearing has begun into allegations that Russian hacking was a factor in the US elections.
Witnesses testifying include former Estonian president Toomas Hendrik, who says Western democracies are under attack.
"These tactics -- disruption of the internet, hacking into parliaments, political parties and candidates, and, more importantly, doxing, or publishing, hacked private correspondence and ultimately spreading false stories or fake news -- represent a new form of aggression."
A former Homeland Security Adviser to ex-president George W Bush, Kenneth Wainstein, has urged the US government to consider launching its own counterattack.
"Simply a recommendation that the government seriously consider the deterrence that is available under the international-law concept of 'countermeasures,' which are unlawful actions that a victim nation can lawfully take in order to persuade another country to stop victimising it. Like, an example being a victim nation hacking back to persuade another country to stop hacking them. "
Concerns over intelligence agencies and electronic surveillance have risen to prominence since Mr Trump's election victory in November.
