WASHINGTON • To United States President Donald Trump, the question of culpability in the explosions that crippled two oil tankers in the Gulf of Oman is no question at all. "It's probably got essentially Iran written all over it," he declared on Friday.
The question is whether the writing is clear to everyone else.
For any president, accusing another country of an act of war presents an enormous challenge to overcome scepticism at home and abroad. But for a president who has been accused of falsehoods and bombast, the test of credibility seems far more daunting.
For 21/2 years in office, Mr Trump has reportedly spun out misleading or untrue statements about himself, his enemies, his policies, his politics, his family, his personal story, his finances and his interactions with staff. Even his own former communications director once said "he's a liar", and many Americans long ago concluded that he cannot be trusted.
Fact-checking Mr Trump is a full-time occupation in Washington, and in no other circumstance is faith in a president's word as vital as in matters of war and peace.
The public grew cynical about presidents and intelligence after Mr George W. Bush's invasion of Iraq based on false accusations of weapons of mass destruction, and doubt spilled over to Mr Barack Obama when he accused Syria of gassing its own people. As Mr Trump confronts Iran, he carries the burden of their history and his own.
As of June 7, The Washington Post's fact-checker had counted 10,796 false or misleading claims since he took office.
"The problem is two-fold for them," said Mr John E. McLaughlin, a deputy CIA director during the Iraq War. "One is people will always rightly question intelligence because it's not an exact science. But the most important problem for them is their own credibility and contradictions."
The task is all the more formidable for Mr Trump, who has assailed the reliability of America's intelligence agencies and even the intelligence chiefs he appointed, suggesting they could not be believed when their conclusions did not fit his world view. This year, he repudiated his intelligence chiefs for their assessments of issues like Iran, declaring that "they are wrong" and "should go back to school".
And just last week, he rebuked the Central Intelligence Agency for using a brother of North Korea's Kim Jong Un as an informant, saying: "I wouldn't let that happen under my auspices."
All of that can raise questions when international tension flares up, like the explosion of the two oil tankers on Thursday, a provocation that fuelled anxiety about the world's most important oil shipping route and the prospect of escalation into military conflict.
"Trump's credibility is about as solid as a snake oil salesman's," said Ms Jen Psaki, who was the White House communications director and top State Department spokesman under Mr Obama. "That may work for selling his particular brand to his political base, but during serious times, it leaves him without a wealth of goodwill and trust from the public that what he is saying is true, even on an issue as serious as Iran's complicity in the tanker explosions."
Iran too has its own credibility issues, and even Mr Trump's critics were generally not rushing to accept Teheran's denial of being involved in Thursday's attack. "Look, it could very well have been the Iranians," said Mr Trita Parsi, a scholar at Georgetown University and founder of the National Iranian American Council. But Mr Trump's "relationship with the truth" is so suspect, he said, it argues for stepping back and not drawing conclusions until there is more evidence.
"With this President, with the country already so divided, even those who support him may not be totally confident that everything he's saying is truthful," said Mr Parsi.