Bernie Sanders. Chip Somodevilla/Getty Images Donald Trump has been hammering home a new insult aimed at Bernie Sanders — and it centers on one word:

"Exhausted."

Trump has posted four tweets since Sunday describing the Vermont senator as "exhausted."

The tweets began after the release of hacked emails from the Democratic National Committee showed the organization to be in apparent favor of former Secretary of State Hillary Clinton during the Democratic primary — while, at times, mocking Sanders and his supporters.

As a result of the email leak, DNC chair Debbie Wasserman Schultz announced that she will resign after this week's Democratic National Convention in Philadelphia.

"Sorry folks, but Bernie Sanders is exhausted, just can't go on any longer," Trump wrote on Sunday. "He is trying to dismiss the new e-mails and DNC disrespect. SAD!"

"I always said that Debbie Wasserman Schultz was overrated," he continued in a subsequent tweet. "The Dems Convention is cracking up and Bernie is exhausted, no energy left!"

Donald Trump. John Moore/Getty Images

In Philadelphia, Sanders supporters have been vocal in their opposition to Clinton in the aftermath of the emails' release. They booed at an event when Sanders told them to vote for Clinton and her running mate, Virginia Sen. Tim Kaine, although the audience cheered during his speech later that night in front of the convention when he pressed supporters to do the same.

"If Bernie Sanders, after seeing the just released e-mails, continues to look exhausted and done, then his legacy will never be the same," Trump posted on Monday.

The Republican nominee has attempted to sway Sanders supporters over to his camp, but polling data shows that only a small fraction of his backers are willing to cast ballots for Trump.

"Honestly, I think he's exhausted," Trump said during an interview with Fox News host Sean Hannity on Monday. "I think he's had it. He wants to go home and go to sleep."

He again reiterated the sentiment on Tuesday on Twitter.

Said Trump: "Bernie's exhausted, he just wants to shut down and go home to bed!"