WASHINGTON — President Trump wants Americans to understand that the economy is doing great, thanks to him. But if in fact the economy sours, then it is someone else’s fault.

Mr. Trump’s Blame List is long. On top, of course, is Jerome H. Powell, the chair of the Federal Reserve — never mind that Mr. Trump was the one who appointed him. Then there are the Democrats, and not to mention the news media.

And on Friday, the president added American businesses to the list, arguing that struggling companies have only themselves to blame and are rationalizing their own mistakes by pointing to, just to name an example, Mr. Trump’s multibillion-dollar tariffs and America’s biggest trade war in generations.

“Badly run and weak companies are smartly blaming these small Tariffs instead of themselves for bad management...and who can really blame them for doing that?” Mr. Trump wrote on Twitter. “Excuses!”