A day after President Donald Trump charged that President Obama had tapped his phones in advance of the November election, his spokesperson indicated that the White House did not intend to offer any evidence to substantiate that remarkable claim—and would not be offering further comment in the near future.

The statement capped 24 hours of intense speculation, as the administration and its allies sought to shift the focus of attention from reported contacts between Trump aides and Russia, to questions about how such contacts had been uncovered. Earlier in the week, Trump and his aides had blasted the leaks which had disclosed the contacts, and the news outlets which reported them; on Saturday, the president shifted to attack the basis of the electronic surveillance that reportedly documented the contacts.

How low has President Obama gone to tapp my phones during the very sacred election process. This is Nixon/Watergate. Bad (or sick) guy! — Donald J. Trump (@realDonaldTrump) March 4, 2017

Later on Saturday, The New York Times reported that “two people close to Mr. Trump said they believed he was referring to a Breitbart News article,” and not to any classified briefings or other intelligence reports to which he might have been privy. Several of his advisers, the Times reported, were “stunned by the president’s morning Twitter outburst,” left scrambling to substantiate the claims, for which the president provided no sources.

On Sunday morning, instead of offering evidence that Obama had ordered the wiretapping of Trump’s phones, White House Press Secretary Sean Spicer issued a formal statement—in what is becoming a pattern for the administration on matters of particular import—broke it apart and tweeted it for good measure:

Reports concerning potentially politically motivated investigations immediately ahead of the 2016 election are very troubling. President Donald J. Trump is requesting that as part of their investigation into Russian activity, the congressional intelligence committees exercise their oversight authority to determine whether executive branch investigative powers were abused in 2016. Neither the White House nor the President will comment further until such oversight is conducted.

In place of the president’s clear and affirmative claims of “Nixon/Watergate” level abuse of executive power, the statement cites only “reports” of “potentially politically motivated investigations.” It does not explain the basis for the president’s dramatic claims.