Republican Sen. Ben Sasse of Nebraska demanded in a statement on Saturday that President Donald Trump further explain his allegations that former President Barack Obama wiretapped Trump Tower during the election campaign.

“The President today made some very serious allegations, and the informed citizens that a republic requires deserve more information,” Sasse said.

He continued: “We are in the midst of a civilisation-warping crisis of public trust, and the President’s allegations today demand the thorough and dispassionate attention of serious patriots. A quest for the full truth, rather than knee-jerk partisanship, must be our guide if we are going to rebuild civic trust and health.”

Trump had fired off a series of early morning tweets alleging without evidence that Obama had tapped his phones in Trump Tower during the election campaign. He called Obama “sick” and compared him to former President Richard Nixon and former Sen. Joseph McCarthy.

“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!” Trump tweeted.

A spokesman for Obama said Saturday that any allegations that Obama had ordered surveillance on any US citizen was “simply false.”

“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,” spokesman Kevin Lewis said in a statement.

Sasse said if Trump was illegally tapped, he must explain “what sort of wiretap it was and how he knows this.”

The other possibility, Sasse said, was that Trump was legally tapped with the authorization of a Foreign Intelligence Surveillance Act court order, in which case a judge would have found a surveillance request credible enough to authorise the wiretapping.

Sasse demanded that Trump obtain the application for surveillance and provide it to the public, or at the very least the US Senate.

Sasse wasn’t the only Republican to speak out on the issue — Sen. Lindsey Graham of South Carolina said Saturday that an illegal wiretap would be “the biggest political scandal since Watergate,” but that a legal wiretap would also be a scandal of the same proportion.

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