ERIE, Pa. — Despite repeatedly stating President Barack Obama was “the founder of ISIS,” Republican presidential nominee Donald Trump said Friday that that he was being “sarcastic” — his latest attempt to blame others for the uproar over what he says.

It's an instinct that Trump's opponents say a president can't possess.

Trump, in a tweet Friday, criticized the “ratings challenged” CNN for seriously reporting his repeated statement that Obama “founded” the Islamic State.

“THEY DON'T GET SARCASM?” he asked.

Trump first made the claim that the president founded the terrorist group at a rally Wednesday in Sunrise, Fla., asserting “ISIS is honoring President Obama — he is the founder of ISIS.”

“He is the founder of ISIS, OK? He's the founder,” Trump continued. “He founded ISIS. And I would say the co-founder would be crooked Hillary Clinton.”

He repeated the claim the next day in Miami — jabbing Clinton as “the most valuable player” for the group — and on conservative radio host Hugh Hewitt's show.

When Hewitt suggested that Trump had meant instead that Obama “created the vacuum, he lost the peace,” Trump rejected Hewitt's softening of his assertion.

“No, I meant he's the founder of ISIS,” Trump said. “I do.”

Hewitt responded, “But he's not sympathetic to them. He hates them. He's trying to kill them.”

“I don't care,” Trump shot back. “He was the founder. The way he got out of Iraq was, that was the founding of ISIS, OK?”

He told a rally later Friday in Pennsylvania he was “obviously being sarcastic — but not that sarcastic, to be honest with you.”

A candidate who soared to the top of a field of Republican primary contenders in part by provocative declarations finds himself adjusting to a general election in which even some officials in his own party have raised concerns about his temperament.

“This is unique in the annals of presidential campaigns, at least in the last 30 or 40 years,” said Martin Medhurst, a communications professor at Baylor University in Waco, Texas, who studies presidential rhetoric. “You can use that once or twice and get away with it, but you can't use it over and over again because very quickly people say it's not sarcasm: it's covering your you-know-what.”

In a campaign, Trump's self-contradictions and corrections provide talking points for his opponent. But loose rhetoric could be “catastrophic” coming from a president, Medhurst said.

“Every word that comes out of a president's mouth is examined. It is parsed for the slightest change in meaning or motivation,” Medhurst said. “A president who conducted himself the way Mr. Trump is conducting himself would throw our diplomacy and our foreign policy into absolute chaos.”

Trump worked to profit on the fuss over his Islamic State remark. In an email to supporters asking them to donate, Trump accused the “liberal media” of telling “outrageous lies about me.”

Almost never does Trump admit error.

One rare exception came this month when he acknowledged a video he said showed a plane carrying U.S. cash to Iran was actually a plane carrying U.S. hostages who were being released.

Most of the time, Trump casts blame elsewhere:

Star of David: In July, Trump's campaign tweeted an anti-Clinton message that seemed to show the Star of David atop a pile of cash, raising questions about anti-Semitism. When Clinton's campaign cried foul, Trump blamed her for trying to “divert attention from the dishonest behavior of herself and her husband.” Also, the media.

Paging Moscow: Last month Trump caused a stir in a news conference by saying “Russia, if you're listening, I hope you're able to find the 30,000 emails” missing from Clinton. Even some Republicans questioned whether he was encouraging a foreign government to interfere in the election. Trump's response later? “Of course, I'm being sarcastic.”

Crimea: Heads spun in the foreign policy world when Trump said this month that Russia wouldn't enter Ukraine, seemingly unaware it already had. When an interviewer pointed out Russia had annexed Crimea, Trump said he meant Russia wouldn't dare go farther if he were president. He insisted he'd said nothing incorrect.

About Saddam: In July, Trump said former Iraqi dictator Saddam Hussein was “so good” at killing terrorists. He also suggested the Mideast would be more stable were Saddam still in power. He took offense that his comments were interpreted as praise for Saddam.

Bloomberg News and McClatchy Washington Bureau contributed.