President Trump’s off-hours recklessness with Twitter sank to new depths Saturday with his unsupported allegation that his predecessor, Barack Obama, had “my wires tapped in Trump Tower” before the election.

In a flurry of tweets, Trump declared, “This is Nixon/Watergate.” “A NEW LOW!” “Nothing found. This is McCarthyism!” He called Obama “a bad (or sick) guy.”

It would have been illegal — and one of the great political scandals in U.S. history — if it had happened. Trump did not present a shred of supporting evidence for his explosive charge, nor did he indicate the source of his information. Was it by viewing direct evidence available to the president, or was he repeating the rumors tossed out by right-wing purveyors of conspiracy theories and innuendo?

The evidence pointed to the latter when the White House later issued a statement calling on Congress to investigate the allegation. If the president had the evidence, he could have — should have — made it public immediately, especially since the charge was denied emphatically by a spokesman for Obama as well as a former director of national intelligence.

Trump’s Twitter blasts are disturbing not just because they are yet another example of un-presidential behavior by a man who has shown little recognition of the responsibilities of office. When a president says he “just found out” something of great consequence, the American people — and allied leaders around the world — should have cause to pay attention.

There are moments in any presidency when the interests of the United States rely on our confidence in the words of the commander in chief. Presidents are entrusted with the authority to launch military strikes, or take other extraordinary action to safeguard the nation, on the basis of intelligence not readily available to the rest of the world. This is not a reality show where outrageousness is the coin of the realm. Credibility is earned by the veracity, not the volume, of an administration’s assertion.

President Trump continues to squander whatever small reservoir of respect he brought to the office.