Sanders has leveled some of his most biting criticism at Clinton in recent days, stirring passions in the race that insiders say could leave the party divided heading into November’s elections.

“While this is the NFL, and everyone understands that it’s a full-contact sport, even in the NFL one gets a yellow flag for a late hit at the knees intended to hurt the other player,” said Democratic strategist Chris Lehane…

The left of the Democratic Party has long been uneasy about Clinton’s coziness with the corporate world. But the emphatic, persistent way in which Sanders is attacking her on the topic risks painting her as a cipher of Wall Street — and such a charge could drain liberal grassroots enthusiasm if she locks up the nomination.

“I am worried about the increasingly harsh tone and tenor of this campaign [that could] turn off Sanders supporters in the general [election],” said strategist Jim Manley, a former aide to Senate Minority Leader Harry Reid (D-Nev.), who has endorsed Clinton. “I’m afraid they’re going to stay home.”