This is being covered as if Trump was merely joking, but I don't necessarily buy that.
Trump spoke this morning where he once again repeated the claim that Ted Cruz's father was involved in JFK's assassination, and the crazy nature of that is what's drawing all the headlines, but Trump also said he might blame his running mate Mike Pence if he loses.
Mr. Trump, seemingly in jest, also suggested that he might fault Mr. Pence should he not win the White House in November. “I ran as an outsider, I didn’t want anybody — Now I have guys like Mike Pence,” he said. “See now if I don’t win, I’m going to blame Mike, right?”
“We have to blame Mike,” he added, as the small crowd in the small hotel ballroom chuckled uncertainly.
Personally I've always assumed Trump would blame his running mate regardless of who it is. He could blame Pence just as he could have blamed Chris Christie or Newt Gingrich. This highlights the insanity of agreeing to be his running mate.
The only thing we know for certain is that Trump won't blame himself. Trump wouldn't blame himself if he were the last person on Earth.
It's impossible to know Trump said this in jest, or if he's serious. Trump himself may not know if he was serious. He is not mentally stable.