Trump provided no evidence to back up his claim and an Obama spokesman expressly denied it.

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Without offering a scintilla of evidence, President Donald Trump on Saturday accused former President Barack Obama of spying on him by ordering the wiretapping of phones in Trump Tower during the 2016 election campaign — a charge the former leader denied. Like much of what Trump tweets, the Obama wiretap claim appears to have followed a path through the pro-Trump media. The president may have been referring to an article from alt-right media outlet Breitbart, which makes claims that Obama worked to undermine Trump during the election. The Breitbart story references a segment from conservative commentator Mark Levin's Thursday night radio show in which he said Obama used surveillance techniques to gather information on Trump. In a series of early morning tweets on Saturday, Trump shared the claims: "Terrible! Just found out that Obama had my 'wires tapped' in Trump Tower just before the victory. Nothing found. This is McCarthyism! "Is it legal for a sitting President to be 'wire tapping' a race for president prior to an election? Turned down by court earlier. A NEW LOW!"

In further tweets, Trump claimed a "good lawyer could make a great case" out of the alleged phone-tapping. He also called Obama a "bad (or sick) guy," comparing him to former President Richard Nixon and the infamous Watergate scandal.

In a statement, Obama spokesman Kevin Lewis expressly denied that the former president or White House officials ever directly ordered such surveillance: A cardinal rule of the Obama Administration was that no White House official ever interfered with any independent investigation led by the Department of Justice. As part of that practice, neither President Obama nor any White House official ever ordered surveillance on any U.S. citizen. Any suggestion otherwise is simply false. The statement only addressed whether the White House had ever ordered surveillance of a US citizen — a point noted by former Obama speechwriter Jon Favreau.

I'd be careful about reporting that Obama said there was no wiretapping. Statement just said that neither he nor the WH ordered it.

Under US law, President Obama could not have simply ordered the surveillance of an individual without first obtaining a warrant from the Foreign Intelligence Surveillance Court, or FISA court. If such a warrant were to exist with regards to Trump, then the president could order it be declassified. Following Trump's tweets, Ben Rhodes, Obama's deputy national security adviser, responded by saying that no president could order surveillance without a warrant.

No President can order a wiretap. Those restrictions were put in place to protect citizens from people like you. https://t.co/lEVscjkzSw

At a town hall event in Clemson, South Carolina, on Saturday, Republican Sen. Lindsey Graham told the audience that he was not sure whether Trump's claim was true, "but if it is true, illegally, it would be the biggest political scandal since Watergate." "The other side of the story...If the former president of the United States was able to obtain a warrant lawfully to monitor Trump's campaign for violating law, that would be the biggest scandal since Watergate," he continued. The senator pledged to "get to the bottom" of the claims.

Graham: I'm worried Trump's accusing Obama of illegality. I'd also be worried if Obama was able to obtain a warrant… https://t.co/NLHsWvdCJo