"In their world, every problem that you can possibly imagine is caused by Barack Obama,” Sanders quipped at a campaign rally in Boston. "If there is rain, if it’s too hot, if there’s a mosquito in the room, it is all Barack Obama.”

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"But we really can’t gloat, because they suffer from a very serious amnesia problem,” Sanders continued. "A serious illness that seems to afflict Republican presidential candidates. They can’t help it, but they just cannot remember the way things were seven years ago."

Sanders reserved his most vicious comments for Republicans, sparing Hillary Clinton, his chief rival in the Democratic presidential primaries.

Watching the GOP’s presidential debate was a “really painful experience,” he said.

"Some of you may have had the misfortune of watching the Republican debate a few weeks ago,” Sanders said. "I promised I would do some tweeting, and I watched it hour after hour and, the energy dissipated my body. It was a really painful experience."

Sanders later turned his comments to income inequality, suggesting the economy is rigged: “Heads they win, tails you lose."

He accused Republicans of trying to turn voters away from the polls.

"Here’s the way politics works,” Sanders explained. "When nobody votes, Republicans win. When large numbers of people come out, when people demand that the United States government start representing all of us and not just a handful of billionaires, when that happens, we win."

"That is what this campaign is about. It is reaching out to our friends and our neighbors. Reaching out to working class Republicans who continue to vote against their own best interest. Bringing people together,” he added.

“When we do that, when we significantly increase the voter turnout, it ain’t going to be a contest, we’re going to win hands down."