On Sunday, Arizona Senator John McCain said that President Donald Trump should substantiate or retract the claim he made that he was wire-tapped by President Barack Obama during the final weeks of Trump’s presidential campaign prior to his election to the White House.

McCain also said he expects there will be more to come related to the meddling by Russia during in the U.S. election last year.

On CNN during an interview McCain said he did not have a reason to believe the allegation made by Trump, which has not been supported with any evidence and which one official in the White House said was prompted by an article on Breitbart, the conservative online news site.

McCain told Jack Tapper on CNN that he did not have any reason to believe there was any truth in the charge leveled by the President.

All Trump would have to do, added McCain was to pick the phone up and speak to the national intelligence director or the CIA and ask what had taken place.

The comments by the senator marked the most recent call from a high-profile personality for Trump to explain the different tweets he released March 4 where he claimed that Obama had wire tapped the Trump Tower. Although, when Trump tweeted his accusations he did not give any evidence to back them up and since then has not supplied any.

However, since the stunning accusations were leveled by the president, several former and current national security officials have denied Trump’s accusations, including James Clapper the former National Intelligence director, as did former president Obama through one of his spokespersons.

Sources have also said that James Comey the Director of the FBI pushed back the claim by Trump as well.

Agencies in law enforcement, under the U.S. Foreign Intelligence Surveillance Act, must obtain from a secret court a warrant to undertake this type of monitoring.

However, communications of Americans might be swept up through the monitoring of foreigners, as in the case with Michael Flynn the former national security adviser, whose leaked communications with Sergey Kislyak a diplomat with Russia led to his resignation.

Reports of associates of President Trump contacting Russians known to the U.S. intelligence community, during the presidential campaign have been dogging the president for a number of months, raising many questions about whether the contact had anything to do with the meddling by Russia in the November election.

Members of the U.S. intelligence community concluded that Moscow has launched a hacking campaign to undermine Hillary Clinton the nominee of the Democrats and Trump’s opponent in the election.

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