Donald Trump has accused US President Barack Obama of establishing Islamic State, now wreaking havoc from the Middle East to European cities.
A moment later on another topic, he referred to the president by his full legal name: Barack Hussein Obama.
"In many respects, you know, they honour President Obama," Trump said during a raucous campaign rally outside Fort Lauderdale, Florida.
"He is the founder of ISIS."
He repeated the allegation three more times for emphasis.
The Republican presidential nominee in the past has accused his opponent, Democrat Hillary Clinton, of founding the militant group.
As he shifted the blame to Obama on Wednesday, he said that "crooked Hillary Clinton" was actually the group's co-founder.
Trump has long blamed Obama and his former secretary of state - Clinton - for pursuing Mideast policies that created a power vacuum in Iraq that was exploited by IS, another acronym for the group.
He's sharply criticised Obama for announcing he would pull US troops out of Iraq, a decision that many Obama critics say created the kind of instability in which extremist groups like IS thrive.
The White House declined to comment on Trump's accusation.
The Islamic State group began as Iraq's local affiliate of al-Qaeda, the group that attacked the US on 9/11.
The group carried out massive attacks against Iraq's Shi'ite Muslim majority, fuelling tensions with al-Qaeda's central leadership.
The local group's then-leader, Jordanian-born Abu Musab al-Zarqawi, was killed in 2006 in a US airstrike but is still seen as the Islamic State group's founder.
Trump's accusation - and his use of the president's middle name, Hussein - echoed of previous instances where he's questioned Obama's loyalties.
In June, when a shooter who claimed allegiance to IS killed 49 people in an Orlando, Florida nightclub, Trump seemed to suggest Obama was sympathetic to the group when he said Obama "doesn't get it or, or he gets it better than anybody understands."
In the past, Trump has also falsely suggested Obama is a Muslim or was born in Kenya, where Obama's father was from.
The president, a Christian, was born in Hawaii.
Trump lobbed the allegation midway through his rally at a sports arena, where riled-up supporters shouted obscenities about Clinton and joined in unison to shout "lock her up."
He railed against the fact that the Orlando shooter's father, Seddique Mateen, was spotted in the crowd behind Clinton during a Monday rally in Florida, adding, "Of course he likes Hillary Clinton."
Sitting behind Trump at his rally on Wednesday was former Rep. Mark Foley, R-Fla., who resigned in 2006 after allegations he sent sexually suggestive messages to former House pages.
