If Donald Trump becomes President of the United States then Barack Obama is partly to blame. Watch the footage of the tycoon being mocked by Obama at the 2011 White House Correspondents dinner. Trump has a giant ego. The Republican candidate is childlike in his self-obsession, and there he was being made to look foolish in front of the power brokers and media elite that has never, in his view, fully acknowledged his supposed greatness. The look on his face is that of an overly powerful man disrespected blatantly for once in public and thinking: “I will have my revenge. I’ll show you.”

That night Obama was rightly mocking Trump for his stoking of the “birther” claims against the President. The suggestion was that Obama was born in Kenya, and not the US, which would mean he was not eligible to be president. That false claim is voiced surprisingly widely, and it was Trump that did more than anyone to bring it to public attention in the US and to keep it there. In tweet after tweet and in his public pronouncements he highlighted conspiracy theories and demanded that Obama prove his birth certificate is genuine.

Now Trump has done something so gobsmacking that even by his standards it is shocking. Just when you might be tempted to think that Donald Trump could not be any more brazen he out does himself in sheer cheek. At a rally today he said:

“Now, not to mention here in the same breath, but Hillary Clinton and her campaign of 2008 started the birther controversy. I finished it. I finished it. You know what I mean. President Barack Obama was born in the United States, period. Now we all want to get back to making America strong and great again.”

As James Fallows of the Atlantic explains, these are simply straightforward untruths from Trump.

First, the Clinton campaign in 2008 did not begin the “birther” claims. They demonstrably simply did not.

And as Fallows says Trump’s statement – “I finished it. I finished it” – is “a flat lie.”

“Trump started this phony and racist controversy. (Racist? Yes. As Bernie Sanders pointed out today, Sanders’s own father, like Obama’s, was born overseas. But Sanders said that no one has ever asked him to prove that he was a “real” American.) And even after Trump claimed to have “finished” it with the appearance of Obama’s birth certificate five years ago, Trump has continued to put out Birther tweets and innuendos.”

What is extraordinary is that so many US voters are not bothered by such behaviour. The attitude seems to be: it’s just one more lie; Hillary is not trustworthy; Trump lies a bit too; they all lie. So what? Forget Left/Right for a moment. That is properly terrifying. It’s 1930s stuff.