Sen. Bernard Sanders of Vermont warned his supporters Monday that President Trump will erase the gains his political revolution has made over the course of the last six years.

In a virtual address to the Democratic National Convention, Mr. Sanders thanked his followers for pushing the nation in a “bold new direction,” and said the stakes are too high this election not get behind presumed Democratic presidential nominee Joseph R. Biden.

“Let us be clear: if Donald Trump is re-elected all the progress we have made will be in jeopardy,” Mr. Sanders said.

“We must come together to defeat Donald Trump and elect Joe Biden and Kamala Harris as our next president and vice president,” he said. “My friends, the price of failure is just too great to imagine.”

Mr. Sanders has arguably done more than anyone else to push the Democratic party in a more liberal direction over the course of his back-to-back bids for president.

Mr. Sanders said working families have suffered and said “together we must build a nation that is more equitable, more compassionate and more inclusive.”

“I know that Joe Biden will begin that fight on Day One,” he said.

He cited Mr. Biden’s support for a $15 minimum wage, expanding pre-kindergarten and transition the nation to 100% clean electricity over the next 15 years.

Mr. Sanders said he disagrees with Mr. Biden’s overall health care views, but said that his approach will expand access to coverage and cut the cost of prescription drugs.